About the Song
Cirno's Perfect Math Class (チルノのパーフェクトさんすう教室, Chiruno no Pāfekuto Sansū Kyōshitsu) is a remix of Touhou background music titled Beloved Tomboyish Daughter (おてんば恋娘, Otenba Koimusume) that is used in a popular vertical scrolling shooter game named Touhou: The Embodiment of the Scarlet Devil. It is sung by miko, composed by Yoshimi Tano, and arranged by ARM. Those three are all from IOSYS, a doujin (indie) music circle. The song tells about Cirno, a character in Touhou series, who becomes a math teacher in Gensokyo and humorously answers the math question incorrectly.