Yasuko to kenji manga

Yasuko to Kenji summary:

[From Ivyscan] Since the death of her parents, Oki Yasuko, a second-year high school student, has been living with her mangaka big brother Kenji, who used to be the boss of a biker gang. Bickering nonstop, their relationship is hardly harmonious. One day in the cram school Kenji forces her to attend, Yasuko falls in love with Tsubaki Jun. But chaos ensues because of the history that Kenji and Jun’s sister Erica share!