It is rape when one party indicates they do not want to have sex and the other continues anyway. It is possible to feel pleasure during rape (from hitting sensitive spots whilst being penetrated, i.e. the prostate or the g-spot), but that does not mean it is wanted. Many rape victims feel intense shame after rape because they did feel pleasure and think something is wrong with them for doing so. (And I haven't read this manga, but this is a stupid question I just had to answer.)
Depends if they are willingly or unwillingly enjoying it. 'Methinks the man doth protest too much' is the mainstay of boys love manga and most of what is read by western readers as rape is actually consensual, just very forced with one partner displaying a lot of resistance to heighten the drama and the emotional content of the sex.
Saying no and not actually fighting back in BL basically means it's consensual as the actions do not back up the words, remembering these are men who are strong and physically capable of throwing off their partner (unlike a woman being raped) and most of the time choose not to. I.e. the protest is tokanistic and not genuine.
In this case it's different as drugs were involved which removed the guy's physical strength and ability to fight back so it's rape even though he was in love with the guy and enjoyed parts of it.
I agree with nyakochan, It was rape even if he was in love with him and enjoyed it... Plus he himself considered it rape so it counts as rape (logically)
how can it be rape, if the other partner is enjoying it...????