Well, ogino did slept with his Senpai girlfriend, so it's both. In nagumo case with the boss, it's stupid move, even though she means good. Still sucks tho, the subversion at the end is just shit.The ending sucks ass.
He spends all this time trying to get with her. She cheats on him. They break up. The end.
No, i guess because of his unhealthy dependency with her. He couldn't focus on his entrance Exam because he thinks of her a lot, this fueled his insecurity of wether or not he could make her happy etc. I guess they continue to date for a bit, based on last chapter, assuming he met the new girlfriend in the office when he started working, they break up in his second year of college.While I do agree that the ending sucks,
Did they break up because she cheated? I knew they both kinda cheated, but i thought it wan't explained why they separated