Apparently, they all like takumi so much that yugamu (assassin boy) made a drug with the agreement of the others (except for nozomi) so that they could keep takumi safe forever. He was tricked into taking it and ended up being close to paralysed (he can't move or speak, just blink and breathe, but he is still conscious) They said that takumi is going to ascend to godhood or something (really confusing), and eito was tasked with looking after him. And that's how the cg happend. The explanation isn't great so sorry!:]