Because of her personality, he felt pressured and less than by being her boyfriend. So he broke up with her, even though that was a big fear of hers. She knew men would find her intimidating because of her ambitious personality. He has grown up now and realized how stupid he was but she is in a relationship now.
I don't agree with the it was the mc's fault. The same thing happened here than with her ex husband, he was to insecure and compared himself to her instead of being happy for her. First ML had some insecurities and felt smaller than our girl. Ofc the communication between then wasn't all great either, if they would've talkit out I believe thing's wouldn't taie this turn. But oh well it's a manga we need dramas( ̄∇ ̄")
does anyone remember why her and kouya broke up ? i forgot