Reading the comments, yikes, guys, c'mon it's not very hard to understand why is Kotone acting like that.
We can pretty clearly see Kotone was raised in environment that forced her to be what she isn't, growing a resentment towards men, mother although could take something as a childish misunderstanding tried to correct her point of view.
Then her classmates thought she was interested in boys but she couldn't say otherwise because it wouldn't be "normal" and obviously not accepted dude to society standards.
Kotone was acting jealous and held grudge towards men is because they took everything from her, she had feelings (albeit, misunderstood) to her friend Risa who was "taken away" by a guy, then the only person who "loved" her in the lowest time turned out to be again swept away by another guy and she tried anything to keep the last person closed to her not be taken away.
Mogumo can feel love towards anyone, it was suitable for Kotone in both "legal" terms as it would be okay for her to marry ze officially and be with someone who appears to be a woman despite having a male body as ze chosen to dress feminine, something she encourage ze to do to fit her desire.
I can understand Kotone frustration, it's not easy to just let go as there isn't "plenty of fish in the sea", it's hard even nowadays due to global society to find someone who could share the same thing as it is kinda socially acceptable.
Hope the author will make her find someone to heal her wounds and make her love once again
Also, Ryuunosuke has a sister, Sakura... seems pretty chill...