Hey! I know. Totally neglecting my other stories that are in progress. (If you haven't read them, check them out! Pretty please?) But this idea wouldn't leave me alone! So here you go!

Summary- Separation Anxiety Disorder:(n.) prolonged, developmentally inappropriate, excessive anxiety and distress in a child concerning removal from parents, home, or familiar surroundings. Mokuba has it, but doesn't know it. So what happens when he tries to sleep over Yugi's? Read and find out! Remember to Review!

Warnings: Possible fluff or OOCness on Kaiba's part.

Pairings: None

Disclaimer- I own nothing! Absolutely nothing! Not Yugioh! Not the song 'Wont Let You Go' by Avril Lavigne! Nothing! I came up with the plot, but that's about it! Don't sue me!

Mokuba was so excited. For the first time Seto was letting him go to one of Yugi's sleepovers! And by himself! Seto had gone to the office early, so Mokuba didn't see him yet. That made Mokuba's chest tighten, but he didn't know why. It wasn't a big deal. The limo came to a stop and Mokuba hopped out, waving goodbye to Roland. He went inside the Game Shop and was greeted by Solomon Mouto.

"Well hello, Mokuba!"

"Hello, Mr. Mouto!"

"Yugi and the others are upstairs, so you can just head on up."

"Thank you!"

With that the twelve year-old Kaiba ran up the steps.

Seto was in the office typing away. He then began to worry about Mokuba.

'It has been years since that happened, but why does it feel like something will happen today? He most likely grew out of it by now.'

With that he continued to work.

Thirty minutes later and Mokuba's chest became even tighter. He almost couldn't breathe! Mokuba tried to play it off and say it was fine but the tightness in his chest had grown unbearable and he couldn't even take in a breath anymore. He began to take short fast breaths that did nothing but made his heart beat faster.

"Mokuba what's wrong?" Yugi asked terrified of the boy's behavior.

"Call-my-brother-please-hurry." He spoke fast his voice small and raspy from being unable to breath.

Tristan grabbed the phone and gave it too Yugi. Tea, Serenity, and Yugi stayed near Mokuba trying anyway they knew to try and calm him. But only one person could do that. Yugi called Kaiba's home office number.

"Hello?"

"Kaiba! Mokuba's over here and he can't breathe! He's shaking and he can't talk we don't know what's happening!?"

When Kaiba heard those words he nearly dropped the phone. A panic attack. "I'll be there as fast as I can, give Mokuba the phone." Yugi laid the receiver against Mokuba's ear.

"Mokuba." Kaiba said, loud enough so Mokuba could hear him, "I'll be there soon, Mokuba. Try and stay calm, okay?" Kaiba said firm. Mokuba stopped trembling some and gripped the phone.

"O-Okay.." Mokuba said his voice trembling.

Kaiba gave a nod.

"I won't be long so hang on, okay." Kaiba said. The call ended and Mokuba began to shake and hyperventilate once more.

Kaiba knew he was most likely speeding, but he didn't care. Mokuba needed him. And he needed him now. Laws be dammed straight to the belly of Ammut.

Mokuba could feel his heart pounding wildly in his chest. He briefly wondered if the others could hear it, but then decided on trying to breathe.

{Yami, what's wrong?} Yugi asked.

[I don't know, Yugi. I have never seen something like this.] Was Yami's answer.

Soon tears were in Mokuba eyes.

Kaiba literally bolted into the game shop and up the stairs. He didn't care who saw him. He was in front of Mokuba within seconds.

He knelt down to Mokuba and wrapped his arms around the small boy just holding him. Mokuba slowly began to calm down. His breathing returned to normal and his heart had stopped pounding, but right now his stomach felt twisted up and his throat burned worse than anything. He buried his face into his brother's shirt crying. Kaiba held Mokuba tighter. "It's okay, Mokuba, I'm here." He said. He picked Mokuba up in his arms and decided to take the boy to the hospital knowing he could have a relapse and end up having another episode. He couldn't risk that happening again.

Yugi and the others looked at each other as Kaiba left the room with Mokuba. Mokuba had looked up over his brother's shoulder and waved them goodbye. But he seemed pale and weaker than when he first came there. "What do you think happened?" Tea asked. "I don't know but let's go with them to make sure he's okay." Yugi said. Everyone nodded in agreement and decided to follow Kaiba to the hospital.

Kaiba knew that they were following him. He didn't care. Mokuba was in the passenger seat, gripping his seat belt and wondering what the heck just happened. He never did something like that before.

"Mokuba."

Weakly, he turned his head towards Seto.

"Do you know what just happened?"

He shook his head no.

"You had a panic attack."

Mokuba's eyes widened. His friend at school had one of those when his older sister wasn't there to pick him up on time after school, thinking she forgot about him, but not as severe as what he had just done.

"Why?" He asked in a weak and small voice. He sounded so fragile to Seto.

"You have Separation Anxiety Disorder. After dad died and we were dumped at the orphanage, you immediately clung to me. I didn't mind. When I had to go to those interviews you would throw a tantrum and sometimes had minor panic attacks. When we were with Gozaburo, you always snuck into my room to say good night. It got better as the years went on, but, I don't know anymore. I think you got used to seeing me at least once a day and when you didn't see me this morning then left to somewhere your mind subconsciously knew I don't normally go, you shut down and panicked." Seto explained. "I was really scared..." Mokuba muttered tiredly. "That's why. When your brain thought I was gone and it had reacted badly. But you never had one this bad." Kaiba said worried. "Never?" Mokuba asked. Kaiba shook his head some. "Never." Kaiba said stern. He parked outside of the emergency care unit than picked Mokuba up in his arms again.

Mokuba was beginning to feel some pain in his chest. "Nii-sama my chest hurts..." He muttered. "I'm sure a lot of your body hurts. You'll be fine though." Kaiba said walking into the hospital. Yugi and the others got out of Duke's car and walked into the hospital as well.

Kaiba explained to the doctors his condition before they would say he had to stay away from Mokuba. They allowed him to go because of Mokuba's condition and didn't want to induce another panic attack. Kaiba sat beside Mokuba as he sat up on the medical table. He looked at his brother worried he was being nothing but a burden. Kaiba could see the worry in his brother's eyes and squeezed his shoulder. "It's okay Mokuba. Your fine." Kaiba said although he wasn't entirely sure about that.

Yugi and the others walked into the room. "Hey Mokuba you feeling okay?" Yugi asked. Mokuba gave a nod although his chest and throat still hurt he kept that to himself though. A nurse walked in and checked Mokuba's throat and reflexes. Then she checked his blood pressure and heartbeat that were a bit high but that was too be expected with these kinds of cases. She scribbled something on her sheet. Then knelt to Mokuba some. "The doctor will be in too see you soon, okay?" She said rubbing his head some. Mokuba gave a nod. The nurse left and not long after did the doctor come in.

"If I may I would like to speak to you for a moment, Mister Kaiba." The doctor asked. Mokuba looked at his brother with begging eyes. "I'm not sure if that's a good idea." Kaiba said. "Don't worry; I'll keep the door open some so Mokuba can see you, and we'll be just outside the door, okay?" The doctor asked. Mokuba thought for a moment than nodded. Kaiba followed the doctor out to the hall and he did keep the door cracked a bit. It was enough for Mokuba to see his brother a little. As long he could see some of him he was fine with it. He would glance at his brother than talk to Yugi and the others some. "I hope it's not nothing bad..." Mokuba thought to himself.

"Mokuba, do you know what's going on?" Yugi asked gently.

"I have SAD, Separation Anxiety Disorder. I have had it since I was small, but never this severe, at least, that is what Seto told me." Mokuba said.

Joey and the others didn't understand, but were trying to. None of them held anything against Mokuba.

"What does that mean?" Asked Duke.

"I am not so sure." Mokuba told them.

"Well, whatever it is, I bet you and your brother will find a way to make it better, right guys?" Joey said optimistically.

Everyone nodded. Mokuba smiled some. Yeah, there was still hope. He looked at his locket and gripped it smiling. He was going to be okay.

"We checked out his throat, vitals are normal, heartbeat was a bit irregular but that's normal with his condition. His throat is sore due to the lack of air entering his lungs. Now there are options for his condition. Your brother's case is a bit rare but it's not impossible to live with." The doctor explained while looking through some of the paper work. "What are the options?" Kaiba asked.

"There is medication he can take that will make the attacks less violent on his system and make them less frequent to happen. However this isn't a cure. You do have to be prepared in case he has another attack."

The doctor said as he wrote up Mokuba's prescription.

"Alright he'll need to start this medication he needs to take this three times a day and with his meals." The doctor explained.

"Anything else he could try?" Kaiba asked.

"Well there is this kind of program that lets kids that have this same disease interact with other children with the same condition. It shows that if they can relate to someone with the same illness as they do they're less likely to feel afraid because they learn from each other." The doctor said than pulled out a piece of paper. "But it's your decision." He said handing it to Kaiba. Kaiba folded it up and put it in his pocket.

"I'll consider it." Kaiba said as he re-entered the room.

Once the door opened everyone held their breath, except Mokuba, who made sure to keep breathing.

"I want to talk to Mokuba. Alone." Kaiba says in a harsh tone. Everyone leaves. Slowly, Seto turns to Mokuba.

"Mokie, would you rather take medicine with every meal or try a program with kids like you and hear what they go through? I want you to pick. Even though neither is really a cure, I want you to be comfortable and make the decision yourself."

Mokuba thought for a minute. He had never liked taking medicine in the past, so taking some with his meals didn't sound very appealing, but neither did talking to a bunch of kids, even if they were like him. He didn't know what to think. If he did the program, then he had to leave Seto. If he took the medicine, he would probably be gagging every day. This was a hard decision to make.

"Seto, which would you do?" He asked instead. His brother always knew what was best for him.

Kaiba thought for a second. He was never a people person and didn't like talking about himself. But he also didn't like taking pills either. Both Kaibas had a nasty gag reflex when it came to swallowing pills.

"I would probably take the medicine. I'm not one to talk about the past. I focus mainly on the future. Why?"

"Then I will take the medicine." Mokuba said with a nod of his head. Kaiba nodded and asked the doctor from earlier for the prescription, which they picked up at the front desk. Once they got the medicine, they allowed Mokuba to go home, saying the familiar environment should help him recover faster.

Once they got home it was time for dinner. Picking up the small, white pill, Mokuba examined it then popped it in his mouth while taking a sip of water. It slid down his throat effortlessly.

"Seto, I didn't gag!" Mokuba announced proudly. Seto smiled at the boy. He hoped Mokuba wouldn't have another attack like the one he had today. Seto had never been so scared in his life. He feared Mokuba would die. He remembered what the doctor told him.

Flashback

"Mr. Kaiba?" A female doctor asked.

"Yes?"

"Your brother was extremely lucky today."

"What do you mean?"

"If you had been even 30 seconds later in calming him down, Mokuba would have most certainly died."

Kaiba was shocked. His brother had been THAT close to dying.

"I applaud you for calming him so quickly. Most cases of panic attack aren't so simply stopped. It usually takes longer, sometimes the patient doesn't make it, and sometimes they do. When you brought your brother, I was prepared for the worst. As I checked his vitals I saw how calm he became. From what I know of the attack itself, there should've been a lot more damage. But I think when you spoke to him on the phone, it told his brain to calm the body down, and start repairing the accidental damage it did to itself. I honestly never saw anything like it. You and your brother are very lucky, sir." With that the doctor left Kaiba alone with his thoughts.

End Flashback

Kaiba was relieved to hear his brother would be okay. That is all that really mattered to him.

One year later

"MOKUBA, LET'S GO! IT IS TIME TO GO TO THE DOCTOR'S!"

"COMING!"

Seto heard footsteps above his head, signaling his brother running around. Most likely looking for his shoes.

Mokuba slid down the railing, landing gracefully on his feet. He smiled and said, "Let's go!"

In the car Mokuba fiddled with the radio, looking for the perfect song to listen to on the way to the doctors. Finally he decided on one.

When you're falling, you're crashing

When your fire has turned to ashes

When you're screaming, your heart is bleeding

When you're feeling like there's no reason

I won't let you go

No I, I won't let you go

Seto began to listen as well. This song made him think of his relationship with Mokuba. They had been through a lot together, Kaiba smiled, and he wouldn't change a thing.

'Cause when you're all alone and it's cold and there's no one to hold

When you're feeling lost, and there's nowhere, there's nowhere to go

When you're feeling sad, don't forget you can reach for my hand

When you're feeling down just remember I won't let you go

I won't let you go (I won't let you go)

I won't let you go

I won't let you go (I won't let you go)

Mokuba began to sing it silently. He remembered in Noah's memory world when he fell and almost died. Seto wouldn't let him go, no matter what. Even after those horrible things he had said to him.

When you're torn down, when you're messed up

Don't you give in, no don't you give up

When you're drowning, and you're fading

Always know that I'm always waiting

And I, I won't let you go

No, I won't let you go

Then he thought about the game the Big Five used against them. He remembered finding Seto chained to the rock and then setting him free, also giving him his deck. He knew Seto would be mad for bringing Yugi and his friends to help, but he didn't know what else to do.

'Cause when you're all alone and it's cold and there's no one to hold

When you're feeling lost, and there's nowhere, there's nowhere to go

When you're feeling sad, don't forget you can reach for my hand

When you're feeling down just remember, remember, remember

Then Mokuba remembered taking the blast from the Five-Headed Dragon. It didn't really hurt, but he saw the anguish on Seto's face when he took the hit, filling his heart with sadness. He remembered thinking, 'You do so much for me, big brother. Now it's my turn to help you.' Then everything had gone dark. When he woke up, Seto looked so happy. Mokuba would never forget that smile. It was small, but it was filled with so much love and pride and a whole bunch of other things Mokuba couldn't describe.

When I said forever

I know that I meant forever

And I won't let you down

I can always be found

And I'm always around

When you're all alone, it's cold, there's no one to hold

When you're feeling lost, and there's nowhere, nowhere

He also remembered at the orphanage, he would run sometimes. He got so scared and didn't think of where he was going, and then he would get lost. Mokuba cried every time. Being five, he didn't know what else he could do. Somehow though, Seto always found him, drying every tear, making him smile, just being the best big brother and father figure he could be. He had promised that they would stay together as brothers forever. Mokuba smiled as he remembered those times, and making that promise. It seemed so easy then. But it wasn't impossible, not for Mokuba and Seto. Nothing ever was.

When you're feeling sad, don't forget you can reach for my hand

When you're feeling down just remember I won't let you go

I won't let you go (I won't let you go)

I won't let you go

I won't let you go (I won't let you go)

Won't let you go

Seto smiled when he saw Mokuba's smile. Everything seemed brighter to him. Thirty minutes later Mokuba and Kaiba were told that his condition was getting a lot better with the medicine. They were going to try sleeping over without seeing each other again, but having a phone with them just in case.

As they were walking out, they decided to go get ice cream. Walking through the park and eating his cone, Seto thought to himself, 'SAD be dammed, I will never let my brother go.' His grip on his brother's hand, not holding the ice cream, tightened slightly. Mokuba squeezed his hand back, knowing exactly what Seto meant.

Neither of them were going anywhere anytime soon. After all, they had a promise to keep, and Kaibas never break a promise.

Wow! That was probably my longest one-shot ever! Thanks for reading! Hope I get reviews from you! No flames! And I promise to work on my other stories as soon as possible!