Yandere Kanojo

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 4-koma and normal page) about having a yandere girlfriend.

(Source: MU)

Included one-shots:
Volume 15: Nekura Musume to Internet (Miss Gloomy and the Internet)
Volume 16: Kinomiya Shoten: Kaiganji Ekimaeten