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 yandere girlfriend.
Note: This is the PUBLISHED version of Yandere Kanojo. The two versions were published simultaneously and were collected in the same tankoubons. They also often reference events from the other.