Basically uke is a masochist and likes getting abused while having sex. He tries to hide this fact and that he's gay. A classmate of his, who is also the son of a certain clinic, notices his scars and offers to treat them. Turns out this seme has a thing for scabs and burns. From then on uke lets seme just touch his body, because he thought it would be "funny". But he ends up always hard by the seme touching him lol

Also if anyone has suggestions on masochistic ukes and weird kinks, I'll take those too.

Tadayoedo Shizumazu, Saredo Naki Mo Sezu by Yoneda Kou. It later than had spin-offs/ squeals. Hopefully this is the one you where looking for and hope you found it by now or come back to see this post XD