This is the struggle I gave Kai: In a fight, he will lock up if someone in the fight has blue hair or looks like a family member or friend, as he's having nightmares about accidently murdering them. In a hostage situation, Kai will lock up and be unable to fight, likely dismissing his blade if summoned. The terror he feels that someone he loves or that is innocent might get hurt by him is paralysing. It would likely take the death of said person, or direct attack on Kai to shake him out of thos state.
I already modified my character sheet with this. Thank you for the help!