SPOILERS
16 years ago, uke was in a car accident that killed both his parents and subsequently lost his memory - got a new identity, new family of fellow orphans, new life. seme was present during accident and tried to save him but was unable to, thinking the little boy didn't survive, he has been tormented by this accident and developed a split personality. In reality, this was no accident at all but something planned by the chairman (seme's father) to kill the parents and kid and steal their aviation secrets which ended up building his company. now the chairman wants to hush everything and possibly kill possible witnesses and people involved.
uke has sex with seme as a "paid prostitute/secretary" in order to help him come back from his evil/crazy split personality
Trigger