I figured it out! The ending sucked (on the second story) because all of their problems were solved during a time skip! What was her editor thinking? They're supposed to stop writers from making mistakes like that...Just trading in one of or two of those emotion slinging pages for development would have saved that story.
I really think this kind of thing is unrealistic... Firstly non of the girls really liked these guys they just wanted sex... Also I don't think that in the real life, boys would fell in love so easily with a girl that just has an obsession with them... They would probably just use her and then leave her... And I agree about the time skip too.
This manga is kind of crappy. I couldn't manage to give a d@mn about a single one of the characters. It lacked nuance or subtlety or something. There were like six pages in the middle of the second story that were filled with nothing but the girl flinging her emotions at her guy. I translated it all in my head to "whine whine blah blah teary love me!" when you get to the end of the story and the guy chooses the main character I was left wondering why instead of being happy for them both.