Katsuki had been tasked with watching a villian while they were in captivity, since the heroes trusted he could handle the villian. At first, Katsuki refused to even talk or look at the villian.. but eventually.. the villian got him to start talking.

Which then lead to eye contact, and the Villian managed to sweet talk Katsuki.. manipulating him into taking off his chains and cuffs.. and Katsuki did.

After katsuki removed the chains, he watched nervously as the villian stood from their chair.. taking off the last of the chains from their body.