He shouldn't have to make up for anything, but with Bunny, he often does. It's because Bunny sulks, Bunny thinks about it over and over again, and so Kotetsu always tries to offer something to take his mind off of it – even if it's himself, as awkward as that may seem.
It was a stupid thing to begin with – damage caused by the virtue of being a hero, of course, but that excuse doesn't fly with Barnaby (or anyone, so it seems). And so in the midst of apologizing, Kotetsu promises to do 'whatever he wants' that night, and oh, that was the kiss of death.
… Or was it actually pretty damned good?
Kotetsu decides on the latter after Barnaby takes it upon himself to string him to the bed, shove him up against the headboard and press his cock to his lips, encouraging him to suck. And Kotetsu does it, tentatively at first – licks and hesitant partings of his lips until Barnaby is fed up with waiting, grasping his hair and pulling his mouth down the length of his cock. He coughs and swallows, eyes flicking upward to watch the blond's expression, which is nothing but possessive and wanting as he rides Kotetsu's face and fuck, it actually feels good being used like this.
He expects Barnaby to enjoy humiliating him a bit more – to string this out and make him wait after Barnaby comes on his face or something like that. But it's far from the case when Barnaby pulls away, twists and flips him in his bindings, shoves him down and fucks him instead, leaves him biting the pillow and clawing at whatever is in reach, probably marring Barnaby's perfect, spotless headboard in the process.
Kotetsu, by the end of it, thinks he needs to keep messing up and irritating Barnaby at work more often.