There's nothing with Ryoko and no incest. So you will see Masuo's sister, mom and grandmother but no animations of them.
Edit:
Oh, wait! I forgot about a feature. You might get your wish granted if I don't scrap that.
Viewing post in LSHT <===> LSHR Update Plans comments
Brother you don't understand the plot if you think Masuo is sleeping around at his own will.
To answer your question, no. He has the ring remember. If that breaks, Reiko will not be his girlfriend depending on the choice player makes. And it will be only implied that she is sleeping with Kunio. No animations. The reason being Masuo is amongst my dearest characters I've created.
Please don't scrap that feature you had in mind, it's not just me but a lot of people want to see Regina having sex, it will be the cherry on top of the cake you are creating, come on you agree with me right that Regina/Ryoko has the hottest body in this game. Still i am very happy, you always reply to whatever i or any other person asks of you, you are very kind LAGS.