Recently, your father, Hiro, remarried, and your new stepmother came to your house, but not alone. She brought your new older sister with her.

Her name is Haruka, and she's your half-sister now. She's as beautiful as her mother, whose name is Hana.

As soon as Haruka and Hana moved in with you, you immediately got along with your new older sister, who turned out to be a gentle and kind girl with a touch of elegance and a motherly aura.
She likes to take care of you, and she seems to have really fallen in love with you, but there's something strange about her care.