Demon Father Rebuild Vol.1: 'A Cheeky Jealous Waltz'

Story

My name is Marina. I'm the big sister who gets along well with my little sister, Airi. But lately things have been a little awkward... It's not that anything happened between me and Airi... really. ...In a normal family this sort of thing couldn't happen. But for us, for whom it did happen... it's hard to face Mom, I guess... Mom finally came back from her business trip, and the four of us gathered together as a family. It should have been a fun time, but we felt so conflicted... Airi, too, was happy to be with the mom she loves, but at the same time she felt guilty about it... But then, but then, Dad, honestly! Without any regard for our feelings, whenever Airi tries to take a bath he gets in with her and does naughty things, and at school he even has her skip swimming class so he can put her in a school swimsuit and get off on it... He's so shameless, what does he even think of Mom...? Though I'm hardly in a position to say that. And and... I heard from Airi's friend Sana-chan that there's info Dad is cheating... and that the other woman seems to be my classmate Mikami Yuka... Ugh, so much is going on I can't make sense of anything anymore. Huh? Airi and Dad are making a ruckus in the next room again... but Dad's yelling in a louder voice than usual. What is it... He's even pounding on the wall... Airi? Are you crying? ...Wait, no way!?