Before we begin, I'd like to thank you all for your patience while I had gotten this chapter prepared to publish. I'd also like to thank Kurama's Foxy Rose and CharmedbyFire for pointing out the error I'd made at the beginning of Mikasa's POV where I'd gotten tripped up and referred to her as Erin while she was talking about him. I've since corrected that error. Now to answer some of your questions raised in the reviews.

1) Although certain events in his life parallel events in the comics, the Hulk I'm using in this story is actually based more off the one in the Marvel Cinematic Universe. As such, his personalities and development are not exactly the same what the the one in the comic universe had reached.

2) The world of Attack in Titan I'm basing this work on is the one that was depicted in the anime rather than the manga (as anime based off manga is often different anyways), and as such I tried to base my assumptions on what was shown in the works that was streamed here in the States on sites like Hulu (which has currently ended at the Female Titan arc), and only used cursory information from the Wiki on the events that followed to extrapolate who was still around and who wasn't.

3) In putting these two together, I'm working on the assumption that the AoT world is actually Earth in the distant future (much like in the original Planet of the Apes), and as such takes place long after the events of the upcoming movie Avengers: Age of Ultron.

As for the rest of the questions, the answers will be revealed as the story continues. For now, enjoy.

Own Worst Enemy

As Erin fought his way through the growing crowd of titans he spotted his objective a short distance away: The fallen top of this district's church's steeple. Erin had hoped that he would have been able to thin out the titan infestation in this area more before he had gotten this far, as his ability would end up virtually nonexistent once he started to carry it towards the hole in Wall Maria. The danger of keeping his path clear of whatever remained would fall to his legion, most of whom are currently trying to lure some of the titans away with their presence while a few of them, including Levi and Armin, attempt to secure a defensible area from which they can set out to clear the titans infesting this area once the hole in the wall was plugged once more.

Of course the ultimate goal is to investigate his old home, where his mother was killed, in order to learn what secrets his father had on the titans, which hopefully would give them the edge humanity needed to take back their destiny from the gluttonous monsters. Erin refused to believe Reiner and Bertholt's proclamation that humanity has no chance against the Titans, and he clung to the possibility that the answer was in his father's basement.

Hearing the distinctive whistle-whir of a 3D maneuvering system nearby, Erin glanced over and was somewhat unnerved yet unsurprised to only spot Mikasa a couple blocks away. The plan had called for a small attachment of their people to watch Erin's back while he carried his load over to the breach in the outer wall, but as usual Mikasa's skill (which surprisingly outstripped even most of the seasoned veterans of the Scouting Legion) enabled her to fight through the titans in this area much faster than the others and get here well ahead of them. Still, Erin felt that it was wrong that Mikasa should be part of the group protecting him even if she had volunteered for the mission: Erin felt that he should be protecting her, just as he had the day human traffickers had killed her family and kidnapped her to sell into slavery.

As Erin returned his focus to the mission at hand he heard something that made him stumble in his advance: The sound of Mikasa's maneuvering system had stopped. He could still hear the whir of the others off in the distance, but he could not hear hers. Erin's first thought was that Mikasa was stopped for a breather, but he dismissed it as she never took breaks while on a mission. That was something that made him both admire and worry about her.

Before he could figure out what the sudden pause was about he heard a sound that chilled him to the bone and stopped him cold: the sound of Mikasa screaming! Even though he did not remember ever hearing her make that sound; not when the titan took his mother, who loved Mikasa and cared for her like her own daughter; nor even when Erin had found her in the custody of the kidnappers, when any other girl would be crying for help; but Erin recognized the screech as Mikasa's all the same. Whirling towards the sound, Erin's worst fears were confirmed. As he saw a titan lifting Mikasa up in both hands, Erin put the pieces together and realized what had happened. Mikasa's maneuvering system must have failed, and that monster had grabbed her while she was still stunned from the fall!

Erin redoubled his efforts to make his way through the horde and get to Mikasa before it was too late, but his presence had attracted far too many of them for him to get through with any real speed. Erin considered abandoning the streets and instead climb over the buildings instead, but he realized that would definitely take too long and Mikasa would be gone by the time he got there. Still, Erin refused to give up, refused to entertain the idea of losing Mikasa the way he'd lost his mother, not when he still had so much he wanted to tell her…

Just when all seemed lost and Erin thought he was about to witness the end of his beloved Mikasa, Erin caught sight of a fast moving….something flying though the air towards the titan and his captive. It was too large to be one of the Scouting Legion, and far too green to be any ordinary titan (and the fact that it appeared to be partially clothed was odd too.) What shocked Erin even more was that even though this variant was 1/4 the size the titan that had Mikasa, it had hit its larger brother with a blow so powerful Erin felt it clear from here! Even when Erin though it all over for the variant when he landed inside the titan's mouth instead of Mikasa, Erin was surprised when the green beast came out on top when it ripped off the titan's head from the inside and toss it to the ground before the falling titan's body dragged the three of them from Erin's sight.

A sudden pain in his lower right leg brought Erin back to his own predicament as he witnessed a smaller titan rip a chunk of flesh from his calf. Taking care of the nuisance quickly, Erin resumed his attempt to make his way over to Erin even as he saw a number of the titans he'd attracted change course towards the new meal. Even though the variant's strange behavior marked it aggressive towards its brothers, Erin wasn't sure that it could be trusted around Mikasa, nor was he sure it was intelligent enough to know how to finish off the titan it took down even as Erin heard it continuing to roar and pound.

When the beast ceased its noise, Erin wasn't sure that was a good sign or bad, but the horde of titans closing in on the location he'd last seen Mikasa in wasn't good in either case. He still couldn't catch sight of her or the variant past the buildings between them, but it was apparent that the monsters would reach where she was before he could fight his way that far. Erin only hoped that Mikasa would find a place to hole up and hide to buy him time to reach her alive.

As Erin continued forward he caught sight of the green variant again as it launched it though the air, bellowing out loudly, "Hulk smash!"

It spoke!? Erin thought to himself incredulously, But how!? Even I cannot speak in this form, and I'm as human as can be, despite my occasionally becoming this….thing. How can it…?

The rest of Erin's thought was lost as the beast made contact with the lead titan and proceeded to tear through them like a scythe through wet paper. Erin never even seen the beast set foot on the ground again, instead leaping from one titan to the next, dropping them quicker than Erin had ever managed himself to do, and moving on before the titan it took down had finished falling. Some it knocked their heads to the side before delivering the fatal blow to the vulnerable area in the nape of their neck with its powerful fists, others it nearly twisted their heads clean off before it finished them. One particularly large titan the variant had ripped the titan's forearm off and used it as a club to smash it in the fatal area before the titan even realized its arm was gone!

As he felt a titan grab him again, Erin realized he'd allowed himself to get distracted once more and he once more went on the attack. Between him and this variant, it wasn't long before this immediate area was cleared of any presence of titans. From the sounds of conflict all around it was clear that the Shiganshina District was far from free of titan infestation, and that would likely continue until the breach in Wall Maria was sealed. However, for the moment the only things standing in this oasis of calm were himself, the variant, and Mikasa. Even though she had a slight limp as she made her way around the corner and into view, Erin still felt himself sigh with relief as he saw she was alive and mostly well. For a moment Erin allowed himself to believe that things would turn out well and that this strange creature would prove a valuable ally as he completed this most important mission. Then those hopes were dashed as the variant turned and snarled at him as it had the titans it took down practically single handedly.

That's just great, Erin grumbled to himself, then as the variant rushed him Erin met his charge head on.

Mikasa's POV

Mikasa was shocked at the variant's strength and savagery. Not only had it managed to make sport of the titans that had given Erin a bit of trouble, but now it turned on Erin himself and was matching him blow for blow. These weren't the bestial blows Mikasa had witnessed from other titans, these were the attacks of someone who knew how to fight and had the strength to do some real damage. Luckily Erin was no slouch either, as he had been fighting most of his life and even did well in his training in the Corp, and his Titan form also gave Erin unbelievable strength.

Then their luck ran out as the variant's size grew somewhat and it began to drive Erin back and ripping him apart! Mikasa didn't know what to make of this, why he was acting like this! Back when it saved her and even gently moved her out of the way, Mikasa had thought that this being might be a friendly. Now it was savagely attacking her Erin, trying to kill him just as it had the other…

Mikasa raced towards the brawling behemoths as the realization had struck her. This variant was attacking Erin because he looked very much like the other titans and it could not tell the difference between them! Mikassa realized that running towards the dangerous conflict was rather foolish and likely to get herself killed, but she would not sit idly by and watch as another person she cared about was taken from her, and since she had managed to get through to this creature before…

As Erin's titan form fell forward to the ground, steam pouring out from where his arms had been ripped off as well as the open wound on his face, Mikasa saw movement in the nape of the neck where the real Erin was even as the variant prepared to deliver the final blow.

"Stop!" Mikasa cried out as she put herself bodily between this 'Hulk' and where Erin laid helpless. As the creature growled at her, Mikasa didn't wait to see his reaction as she drew her swords and turned away in order to cut Erin free from his titan body. She couldn't help cutting off his hands in the process, but it went much better this time now that she was more acquainted with how he was situated in his body. "See?" Mikasa cried out to the Hulk creature as she protectively embraced Erin's stirring body, "Erin isn't like the others you had beaten. He's my friend, you can't hurt him!"

The variant glared down at them for a moment, then it hopped down and backhanded Erin's disintegrating titan form in the face, causing Erin to wince as he was still partially connected to it. Then the creature turned its back to them and arched its spine as it bellowed out loudly, "Hulk is the strongest one there is!"

Was that why it did this? To prove that it was stronger than Erin and the other titans? Mikasa thought to herself, then she dismissed the idea as she recalled that had chosen to protect her rather than charging mindlessly into battle. Whatever this Hulk creature was, there was certainly something human-like about its feelings and thought processes.

Still, this incident had certainly set them back in their plans, and Mikasa would not let her concern for Erin distract her and allow her teammates to die needlessly. Pulling out her signal flare gun, she loaded and fired a series of signals into the air: First black, to let them know a deviant-type titan had been encountered (though she knew she'd have to explain Hulk to them later), then yellow to let them know the mission was currently terminated (Erin could not continue in his state, and the mission hinged upon him), and finally blue to tell them to retreat to the secure location.

Once her duty to the other was fulfilled, Mikasa finished freeing Erin from his decaying body and helped him lower down to the ground below. Once Erin had his feet securely beneath him and showed no signs of falling over, Mikasa approached the variant and cautiously placed her hand on his arm. Once it had looked at her, Mikasa gently said, "Uh….Hulk, was it? Thank you for saving me earlier." When it made no response, Mikasa continued, "Listen, I've got to get my friend back to camp. I don't know if you've got somewhere to go, but if not, then would you like to come with us? It should be pretty secure there by now, and the titans shouldn't bother you there."

The Hulk nodded, then Mikasa went to support Erin's weight so they could move more quickly down the street. Hulk easily matched their pace, and though he would occasionally look over his shoulder and growl, there were no other incidents as he followed along behind them.

As they reached their destination, an abandoned Garrison building recently refortified, Mikasa noted a couple of Survey corps members standing guard on the roof. Their eyes widened at the sight of the Hulk, but Mikasa waved them off before they could sound an alarm or attack, and they simply looked on in confusion as she went inside.

Once past the door, Mikasa saw Armin and Levi leaning over a map of the area, and Mikasa was delightedly surprised once again at how quickly their friend had become a valued member so shortly after his joining. When he saw her, Armin looked up with a smile on his face and concern in his eyes as he took in Erin's state and said, "We saw the flares and guessed from their grouping that things did not go according to plan. That looks like we were correct, what happened?"

"We ran into a….complication," Mikasa explained as she gestured towards the door and Hulk stepped inside. Everyone pretty much gasped at once and reached for their weapons, while Touma exclaimed, "What in God's name is that thing!?"

As Hulk growled back at them, Mikasa placed a placating hand against him as she called out, "Everyone calm down and put away your weapons. His name is Hulk and he saved my life, but he doesn't take confrontation very well and I'd like us all to remain friendly and not die, okay?"

Everyone took the hint and sheathed their swords, though they still eyed Hulk very warily. All except Zoe, of course, who seemed to take Mikasa's proclamation that Hulk was friendly as an invitation to approach him with her usual enthusiastic curiosity that had others often thinking she was off her rocker.

"Fascinating!" Zoe practically crowed as she came in and examined Hulk from practically from every angle much closer than Mikasa would recommend her doing with any normal Titan, much less a variant like this that was unrestrained, "This variant is unlike anything I had ever seen or even heard of! I would love to know what factors resulted in this unusual skin tone."

Rather than becoming agitated or reacting violently like Mikasa had feared he would, Hulk instead got a confused look on his face as he bent down to look Zoe in her face and asked in a gentle voice, "Betty?"

Zoe leaned back in surprise, then she turned toward Mikasa and asked, "He can speak?"

"Not very well, but yes he can," Mikasa confirmed, "He also seems intelligent enough to understand things. He's extremely strong, though, practically ripped apart several titans four times his size in no time flat and would have killed Erin too if I hadn't stopped him, so be careful. Okay?"

Zoe's eyes widened at this information, but Mikasa could tell that it was from increased curiosity and excitement rather than fear as Zoe nodded vigorously then turned back towards Hulk and asked, so where did you come from, Hulk? Can you tell me how you came to be this way?"

Hulk must have found Zoe's enthusiasm as exhausting as the rest of them did sometimes, or the battle had taken more out of him than Mikasa had noticed, for he yawned as he said, "Hulk tired. Sleep now." He then turned and bulled past a table towards an empty floor space near one wall, the corps members over there parting before him and giving him a wide berth as Hulk curled up there and glared at them one time in warning before he closed his eyes and began to breathe deeply.

Once it became clear that Hulk was asleep and wasn't going to bother them, some of the corps members came over to treat Erin's injuries while Levi asked Mikasa, "That Hulk character nearly killing Erin, that the complication you mentioned?"

"Part of it," Mikasa confirmed, "Also I'll need someone to check out my maneuvering gear, as I was nearly killed when it failed on me. Erin would be picking me out of the teeth of a 20 meter titan if it weren't for Hulk pounding it into paste. I think it only attacked Erin because it believed he was like the others."

Levi nodded in understanding as he said, "We'll have to wait for Erin to heal and recover before we can try again, but do you think we can count on Hulk's help when that time comes?"

Before Mikasa could come up with an answer, Zoe interrupted them in a tone that did nothing to disguise her fascination, saying, "Mikasa, look at this!"

Mikasa look where Zoe was pointing, and for once she shared her fascination at what she was seeing. Before her eyes, Mikasa saw Hulk visibly shrinking down to more human proportions, his musculature also visibly reducing as his skin tone changing from green to Caucasian. His reversion to human was quite unlike Erin's or Ymir's, where they emerge from their Titan body and leave it to disintegrate like any dead Titan, but before long in Hulk's place was a scrawny adult male that looked much like a grown up version of Armin with dark hair. The man woke up and looked around in confusion until his eyes fixed on Mikasa, then he asked, "Where am I? Who are you people?"

Mikasa briefly exchanged confused looks with Erin, Armin and Levi before looking back at the man and asking, "You don't remember how you got here? Are you feeling okay, Hulk?"

" 'Hulk'," the man sighed as he nodded in understanding, "You guys had met him, I see. I'm surprised to see this place not looking like a bomb was dropped on it, to tell the truth."

" 'Him'?" Mikasa asked him, confused at the distinction the man had just made, "Just who are you, mister?"

"My name is Dr. Bruce Banner," the man answered her, "I can see that we each have a lot to talk about."