Domestic na Kanojo
ドメスティックな彼女
High schooler Natsuo is hopelessly in love with his cheerful and popular teacher, Hina. However, one day at a mixer, he meets a moody girl by the name of Rui and ends up sleeping with her. Soon after, his father announces that he's getting remarried to a woman with two daughters of her own. And who shows up in tow, other than both Hina and Rui?! Natsuo's outrageous new life starts now!
not blood related though
Insert incest joke here
The anime is undeserving of such an amazing opening
Wow…. the description intrigues me ( ͡° ͜ʖ ͡°)