Sam Crane's manga / #student x student(150)

It came out in the lines of something like Cruel Intentions

I think the beginning was a bit confusing (after some time you understand or accept the explanation about the new student blackmailing him with a photoshopped picture), but what's hard to comprehend is his reaction to the guy's advances. I mean, you may understand what draws them together, but you don't quite feel it, I think the author failed to pass it to the readers.