Chun Mo Rionnag:
I had read the manga before watching the series, so I knew what was coming. Kirino's choice is a disastrous one which may lead him down the same path as Sensei Yanagida, IMO. Living your life to please others is not a path to happiness.
I agree. I couldn't get at the moment why Kirino acted "okay" with Mishima and then took that choice of leaving their friendship and HERSELF behind, but giving a second thought on his reaction, he may just decided to leave everything in "good terms", idk. His mom was trying to understand and accept him, so I don't really get it. Maybe it was an "I'm done giving her deceptions and problems, so whatever, I'll give this expected-perfect-life-of-son to her" ??
No matter what, that's pretty sad.