It was the day Chiichan, who never comes to middle school at all, suddenly showed up in her tattered sweats with dead insects, causing a commotion in the class. Yuua has been with her since kindergarten and cares about her, and her classmate Koudai asks if he can help Chiichan out... A new series born from a unique collaboration, in which Oshimi Shuuzou depicts the prequel to Chiichan, the aberrant heroine of Naitou Eisuke's film *Poison Girl*, as an original manga *Chiichan*!