Responses
It's called being lovesick. Letting yourself die because the person you love rejects you is a pretty old trope in fiction (very common in classic literature)... You can't be mad at an adult man for going into depression, whatever the trigger for said depression might be. Even if you hate his guts...
I like, that he got a taste of his own medicine.
I don't feel bad for Kou. It's not like he accidentally hurt Shinobu, he set out to break his heart and toss him aside. I'm just glad that he wasn't forgiven so easily, but also mad that a grown man can't take care of himself just because he's being rejected. He is selfish but the uke will forgive him now that he has collapsed. I just want Shinobu to be loved and cherished and if he gets that with Kou then fine.