Responses
I went back to check, it's the second chapter. The rehab was him getting over his dislike for women I'm pretty sure which was what they were talking about when they got to Tokura's place and the reason he used to make Tokura let him off the hook (I could only tell you this, you really helped me out etc.) but I think the rehab method he had in mind was sex.

Ryo mentioned rehab in the 1st chapter (or 2nd I don’t remember anymore) and that was never brought up again... What did he go to rehab for? Im genuinely curious
Btw THIS IS DEFINITELY ONE OF THE HOTTEST YAOI I HAVE READ SO FAR I MEAN LOOK AT BOTH OF THEM and the sexy scenes? TOP TIER ლ(´ڡ`ლ)