Koichi Kuwagata (Ryuta Sato) is an associate professor for literature at a third rate university. He has lived a dull life up this point and now decides to live a stylish life and, in the process, takes on difficult to solve cases in and out of the university. Unable to solve the cases by himself, Koichi Kuwagata relies on the help of homeless female student Hitomi Kanno (Nanami Sakuraba) with her excellant reasoning abilities. Meanwhile, Professor Koichi Kuwagata uses his own delusional skills and can understand the thoughts of the criminals.

A professor falls from a window at the university. Rumors swirl among the students that in the room where the professor fell, a strange incident called "April Ghost" took place. The night that the professor fell, the temperature was unseasonably cold and it snowed. Dean of the university Tsuyako Kujiratani (Mitsuko Baisho) asks Koichi to figure out what the "April Ghost" is.