Kare wa, Imouto no Koibito

Other name: 彼は、妹の恋人 , He’s my Sister’s Boyfriend , My Little Sister’s Lover

Synopsis:

Ishihara plays a timid florist, frustrated with her non-existent love life. While down on her luck she runs into an old classmate (and crush) of her’s on the street. Things are going great when her younger sister, who has taken away every guy that she’s ever liked, begins to weasel her way between them. Can Haruka overcome her obstacles and fight for the man she’s loved since highschool?

Also known as: 彼は、妹の恋人 , He’s my Sister’s Boyfriend , My Little Sister’s Lover