TLDR MH Aya got groomed by uncle while BF Satoshi was too busy that he didn't even kiss her or spend time with her because he was studying get into college with the promise to go out once he gets admitted and he did, meanwhile uncle took advantage of MH after raping her behind his back.
The turning point for them was BF canceling the long awaited date she really wanted to because his family came by so she went for the one who always was looking after her, her uncle. Uncle decides it's time to end this all and calls boyfriend to his place there BF finds Aya asking for dick but does jackshit as uncle fucks her, he just watched instead as he later realizes he let it go so far his relationship is done for (she even asked bf if he still loved her after looking at her being lewd now and the idiot BF spilled spaghetti again letting uncle to keep fucking her more) then gets a pity BJ, I mean who the fuck argues with someone fucking your girl lmao, usually they would stop it and then talk if not beating the shit out of the cheaters, well hentai logic as usual from this author I guess, he even copied a previous work of his to a T.
He begged her to not break with him, humiliating himself further, that he would accept everything from her but it's too late, she was cold to him and at the same time had a bright face whenever she looked at the phone messages from her uncle, still he didn't do anything, followed her meeting with her uncle, they had sex in the bush as MC watched and then masturbates until to hear from uncle she's pregnant and that she loves and will marry uncle, says her farewells to MC. Time skip and he is dating another girl but still isn't over his ex who passed by pregnant and leaves to masturbate at home.
Also the extra pages is weird, after breaking up and time skip she still wonders what would ex BF say if he saw her having pregnant sex.