Ace was not handling his recent life well. He had accepted his death. He was devil spawn and didn't deserve to live. He'd heard it through his whole life and knew this was how his story was always going to end. Sure he wished to survive, wanted to continue living and being part of a family but he was shit out of options to fight and it would almost be a relief to not have to keep struggling. He hurt, and no longer had the strength to keep pretending the Marines hadn't won.
Then Jinbe was thrown in his cell, explaining that Pops was calling his allies for war and suddenly he was filled with fear and a new wave of self hatred. Why couldn't they just let him go? Had he not brought this upon himself by running off against his Pop's wishes? Still this fear was nothing compared to the terror he felt when Boa Hancock informed him that his baby brother was in the prison.
He was in agony. Luffy needed him, was in danger and being hurt for him, and there was absolutely nothing he could do. Ace swore, he raged, he prayed to a god he didn't believe in, he begged for it to be a bad joke. But eventually he could hear the anger and fear in the guards voices, he could feel the chaos in the walls. There was no denying his brother was there and wreaking havoc as only Luffy could. It was too late though. He knew the guards were coming for him. They were going to take him away and leave his sunshine brother here in the dark, terrifying hell that was meant for demons like him. Not for Luffy, never for Luffy. In his last moments he begged Jinbe to help Luffy. To put his strength, power and loyalty behind the last good thing Ace had. Jinbe may have declined, refusing to give his loyalty to people who hadn't earned it, but Ace knew that would be no problem for Luffy. It was the last thing Ace could do to help him.
Then Ace was dragged out to the transport and Magellan himself told him that the kid had made it to Ace's cell, that he had been so close to seeing Luffy again. Told him how they were trapped and being gassed, that Luffy was already poisoned and dying slowly. Ace fought to go back… and once again he was defeated. Then he was sailing away, leaving his brother in his place. He should have died earlier. Should have been killed before he could infect others lives. Now his Pops, his Whitebeard family and his baby brother were all facing death and pain.
He had been lost in his despair and self loathing when he felt a tidal wave of pressure break on his mind. Submit, don't fight, submit, death, submit, darkness. Part of him longed to follow the power into unconsciousness but he still struggled to hold on. Time flew by and yet dragged on endlessly as he fought to stay aware. He blinked desperately trying to clear his vision when he saw a form in front of him, only able to identify the human shaped blob from his distinctive red hair. The urge to submit still burrowing in his brain, despite Shanks no longer actively using his haki. His mind was a mess and it was impossible for Ace to focus on anything.
It took a good 10 minutes before his brain kicked back on and he dove for the door, desperate to get out and force the ship to go back for his brother. Apparently the doctor had an issue with his sudden movement and he had ended up clawing and biting at the older man who was pinning him back on the bed. "You're going to hurt yourself kid. Hey lay back down! You need to stop struggling! We're trying to help you!" Grunted the doctor as Ace chomped down on the man's arm.
Suddenly the door flew open and there was a crack of power that froze them both. Ace stared up at his little brothers idol and prayed that the man was worthy of that honour. "No! You've got to turn around. Please! Luffy is in trouble." He spat out desperately. "That goddamn idiot tried to save me. He's in danger. Luffy is in Impel Down and I don't know what's happened to him."
It was a relief to see the obvious horror and panic in Shanks' eyes. Finally someone in a position to and powerful enough to help, understood that this was a fucking emergency. Then everything went dark. Ace came to and looked up to see Shanks in what could only be a panic attack with his first mate coaching him back to stability. The sheer power that he had thrown off boggled Ace's mind and he realized that earlier he had only been using a fraction of his power. Ace gave thanks that this man was on their side. Facing him in a battle would be suicide.
Ace wanted to cry when he watched Benn run off to tell the crew to head for Impel Down. They were going to help. They WOULD be on time… he wouldn't accept anything else. Ace didn't even care that Shanks made him go over the worst days of his life, again and again. Instead he desperately searched his memories to see if there was any small detail that he missed, anything that would help save Luffy.
Finally it seemed Shanks had decided he knew nothing else useful and he went to leave the room before hesitating and looking back. "Ace stop resisting and listen to Hongo. Let him treat your injuries. Hongo, do what you need to do if he gives you any more problems."
Ace squawked at that but Hongo gave him a satisfied smirk. "Great. Let's fix you up before I get your brother too. Now you going to cooperate kid or shall I get out the drugs?