First girl, is the PC's sister-in-law the second bruntte is his actual sister, I say it's Netorare, the game is spot on about trying to humliate his never seen brother and steal his wife.

I see some other GokuFero games with this error as well, sister-in-law being mistaken by sister, and often ignoring the Netorare theme as well.

Base +2, ggggehent +9

http://www.getchu.com/soft.phtml?id=691067&gc=gc
First girl is indeed the sister in law (wife of hero's brother), but the girl with the yellow ribbon in her hair is the woman's twin sister, and thus making her no relation to the hero.

Base +2

both girls are awesome thanks

Base +3