Responses
That seemed consensual to me, Makoto even asked to be friends with the guy afterward. That demon told Makoto why he was there and how sex would result in him losing his human smell (that would have made him vulnerable to other demons as we saw way earlier).
Makoto understood he needed to rebel against J bc he never said he wanted to be a demon, J was doing it against his wishes and seducing him to go with the flow. J was pleased Makoto kept his own mind but he made a show of punishing him by ripping his head off again..but I think j did it to deaden Makoto's senses enough he didn't go mad from sex with the snake schlong. Ymmv
This is weirdly enough a story where the rape scene is necessary and moves the plot forward. The demon world is so twisted and dark. They follow rules that go against all human comprehension. What happened to the MC was part of trying to rid him of his humanity.
He's growing powerful at an incredible rate. You'd think his master would fear that, but he loves seeing how powerful the kid becomes.