Sorry, but did I just hear you say that Souichi must be blamed because he's too much of a tsundere and that he must also be blamed because Morinaga is too much of a possessive and rapey guy? Hypocrisy much?
On this point of view, it was Senpai's fault that he made a choice of being partners with a person that he raped (violated, whatever) him... Also, we are talking about a MANGA, about a fantastic situation so we can think with a realistic, straight way because almost nothing is normal -or acceptable- in the yaoi universe, if we transfer all those shitty situations in real life. I'm not talking about the gay part, but about how the most of these relationships go with the flaw, forgive, accept everything etc.
I'm sooo tired with this manga and moreover with Senpai. Ok... he is a tsundere, and I love tsudere characters, but, come on... I need a little more character development and for sure, not a man who is being so much cruel to his partner about nothing.
If I was Morinaga, I would -probably- have ended things a long time ago.