@DY4Y
Mind you I havent read all of them, but by the time I stopped reading Sena and MC started dating (which was quite subversive at the time, because the entire plot had driven him towards Yozora). Yozora became a total self-destructive trainwreck before that, admitting that a lot of what she had been doing was due to her issues and from what I remember Sena and MC were trying to help her recover.
I don't care much for het romance and I definitely saw Sena as fiercely bisexual, but from what I remember it all made sense in its own way. I do wonder how it actually ended.