If am kousuke, at this point i will never forgive koto for abandoning him like this. Okay yes you are a high school girl and have an unstable mother so maybe she does not have the courage, but you are the one who initiated this relationship and when things starting to crumble she is trying to play victim by becoming regretful to her mother instead helping kousuke. Kousuke try to reach Koto by showing his intent to help her relationship with his mother, then this bitch right here just staying silent and even reaching out miwa.
I hope kousuke will abandon her, cause at this point it only shows that Koto did not take this relationship seriousoy enough.