
When they were filming they drugged kyousuke but it was too much for him and it left him in shock. I think that the drugs along with the trauma led to amnesia.
They probably were filming him as a way to put on a setting for Itou to kill him, make kyosuke suffer by doing that infront of the man he loves, and for the asshole of a boss to keep it as a prize and relive the moment.
I am not sure why but, I guess Itou wouldn't want to force kyosuke into doing anything he doesn't want to do, Why would he force his feelings? Itou slowly got into his life and in a way gave kyosuke a choice, to fall in love with him again or go on and make a life of his own.
I'm sorry if I didn't explain myself well... (=・ω・=)
In the end why did Kyosuke lost all of his memories? He asked the 'boss' to keep his memories and in exchange he'll take responsibility for all the troubles that he did right? But why on earth cant he remember a thing now? Why are the 2 dudes filming Kyosuke while f*ckng him, what is their goal in doing that? And why did Ito-san kept his past and their past relationship a secret? please help me i want to understand that part T-T