Why did she want to break up with him again?
I didn't see the transition point that suddenly made her want to dump him...?
shareShe was getting fed up of how he usually kept her in the dark of things, not knowing what to expect as he doesn't bother to express anything, and she just had to experience his (and his parent's) plans for her. But also, she wasn't being heard.
His 'keep your problems over there, and ill keep mine over here,' isn't something for her favor. Ignoring her when she said she got lost in the mountains was a little sad, but perhaps he didn't sympathize with her because she chose to be alone in the natural terrain of "foreign" territory. But my best bet is he was taught being raised that youu just shut up about your experiences or what has bothered you. He didn't mind her being independent, but if he's and his inner circle is not of an assertive, that is something not to entertain.
I also think she thought his "loving" her was kind of ironic. She loved Japan and even wanted to be Japanese. Then she found out that he was a France fanatic and even had a France fanatic club with his friends and saw how he wanted to be French and go to France.
She tells her friend something like "I'm scared. I'm scared that to me he's Japan and to him I'm France." Like, the only thing attracting them to one another was superficial. After that dinner with his friends when he put her on display the entire night, it was clear to her.