I mean, he brocon sis was not unwelcomed, but going for the forced kiss may have been pushing it too far.
That being said, Sana is cute in her own way, just wished she would stop calling herself in the third-person.
Apparently people dropping this because of that ??!! How are you turn off by this after the whole nonsense sensei accepting his confession, and the fact that a 30 yo man is so shy with is GF, and he is from the future, even so, he acts as he knows nothing? He should already know how her sister is ...
All I'm saying is that there have been other plot holes far more disturbing than a brocon sis, so I don't get you.
Wait for an explanation, don't drop it so soon, since you already have been brave enough to get through 10 chaps