Sister Breeder

Episode 1 - 3 - Sister Breeder
Shouta is very affectionate towards his sisters Rena and Aina, they grew up as close siblings. Day by day, he becomes more affectionate towards Aina... and eventually he even sneaks into her room at night!? Rena tries to stop Shouta, but ends up receiving his affection in Aina's place. Due to her hidden feelings for Shouta and the pleasure of experiencing things for the first time, the once innocent Rena is steadily being trained by Shouta...!?

Episode 4 - Akuma de Kanojo wa Boku no Tenshi
This is a forbidden love. Timid teacher Makoto tries to suppress his feelings for his student Mano. But one day, Makoto finds out Mano's secret, and with an angelic smile, she starts making devilish demands! Mano seduces him with various types of play. However, in order to melt away Makoto's hesitation, she provokes him into serving her...!? A pure love story of a devilish angel!

(Source: Lune-soft, translated and edited)