Tanaka Manabu is a geeky student, on the way to school he meets a girl carrying a bloody bat. That girl is Ryuuzaki Reina, leader of the school's female delinquents. It's love at first sight. A gag manga (with a combination of 4koma and normal page) about having a yankee dere-dere girlfriend.

Note: In the title of this series, "yandere" isn't refering to this term, but to the "yankee"+"dere-dere" combination.
Yandere Kanojo came out in two editions. One is the "magazine version", Yandere Kanojo (Joker); and the other one is the "online version", Yandere Kanojo (Online).