That Chekov made it this far in life with so little exposure to the gruesomeness of death is, in a way, remarkable. Home hadn't been exactly been a peaceful place in the last five years, and the City--the first prison--had been prone to more violence and chaos than MarinaNova. He had died in the City (something he wasn't in a hurry to mention to Kirk), but that had been... easy, almost. No guilt, no wondering after the fact if he had done the right thing or if he could have tried something else to end things peacefully.

Starfleet Academy taught its cadets how to defend themselves and how to fire a phaser. No one mentioned how awful it felt to snuff out a life.

When Kirk returned, Chekov was kneeling by an open panel and toying with wires, already succumbing to his thoughts. (Another thing no one bothered to tell him: having a quick mind that could follow multiple trains of thought at once was never beneficial in situations where thinking less was necessary.) The order pulled him out of his head and he jumped to his feet to follow Kirk. Commands, good. If Kirk was telling him what to do, maybe he wouldn't have time to think.

"How badly hurt are you?" he asked, disappointed in himself for not asking before leaving Kirk outside on his own.