The mere idea of Luffy dying was enough to drive him near insane.

He tried to keep quiet about it. He talked about Luffy all the time, of course- how kind he was, how powerful, how he was going to become the pirate king- but he kept the fact that Luffy's existence was literally keeping him alive on the down low. That he'd die for Luffy in a heartbeat.

Dragon was one of the few people who had some idea about this. He scolded Sabo for it all the time. That he should never be so dependent on a single person's life, that he shouldn't let a single person being in danger make him fly so far off the handle…but Sabo couldn't help it.

His devotion to Luffy wasn't just about Luffy being his little brother who he loved dearly, though that was certainly part of it. It was about how he couldn't live with the guilt and self hatred if Luffy were to die. That combination of sickening melancholy and sadness combined with the guilt- it'd tear him to pieces. If it didn't kill him, it'd make him go mad.

He'd rather it kill him. He knew from experience that when his brothers were threatened or so much as insulted, red clouded in front of his eyes and he lost control of his hands. When his vision cleared he often found the landscape around him pummeled and the dark stain of blood soaked through his gloves.

It scared him.

Of the things Sabo wanted to be, violent was not on the list. Dragon had told him not to maim or kill unless absolutely necessary, and he had taken that to heart. He truly believed in not holding grudges and that life deserved to be preserved. So why did those values decide to escape his body as soon as Ace or Luffy were brought into it? It was disturbing. He couldn't stand the idea of what he'd do to those around him if Luffy died, seeing as merely threatening him made Sabo's brain re-hardwire itself into kill mode.

Perhaps it was a sort of defense mechanism. He had nearly died from the pain and turmoil of Ace's death, after all. Some primal part of him wanted to protect himself from feeling that pain again, no matter the cost.

"I'm a monster," he said to Dragon one day, when they were sitting by the beach together, talking about future plans for the army.

Dragon laughed. "You are not a monster, Sabo. I've met monsters. You're nothing like them."

"Maybe not, but I become one. When someone insults or tries to hurt Luffy, I can't…if you saw it you'd understand. I even scare myself. It's…horrifying."

"I've always told you that I think your love of my son is one of your more unfortunate traits," Dragon said. "It's very sweet, but very dangerous. If it's making this happen to you, what can you do to stop it happening?"

"Kill myself."

"Sabo-"

"I'm serious, Dragon-san. I feel like if I wanted to, that'd be the only way. I don't know if you're under the impression that I can somehow choose to love my brother less, but you're wrong. I can't. I don't want to, really- when it's not making me go half insane with blood lust my love of him is one of the things that makes me happiest. My time spent with Luffy…is the happiest time in my life. I can't give it up and hurt both of us."

"Then I suppose you'll have to accept being a monster," Dragon said, and his tone was only slightly sarcastic.

Sabo looked down at his hands. They twitched a little, as though even when he wasn't fighting they itched to form claws. "I'm loyal to you, Dragon-san, and I am deeply indebted to you. But if you were to have Luffy in your arms and say you were going to kill him for whatever reason, I'd murder you in a heartbeat. Without a second thought. At least, I'd try to."

"I know. I don't like to think about it, but I know that. I always have."

"I'm sorry. I don't know why I'm the way that I am. But I can't let Luffy die. There isn't anything I wouldn't sacrifice to keep him alive, not my life or anyone else's. That's scary. That's fucking terrifying to me. Still…I love him, Dragon-san. It's not all dangerous or sick. I really do love him."

Dragon put his arm around Sabo's shoulder and squeezed him lightly.

"I know that, too."