Frequent disappearance of panties incident. Not only from gym lockers and laundry at home, but also women's underwear robbed on the streets at night began to occur. Meanwhile, a large amount of women's underwear was discovered at a boy's school. It is suspected that it is related to a series of serial theft cases, but because the school is a sanctuary, an undercover investigation will be carried out in absolute secrecy. Then, the one who picked up the arrow was Aoi Tsukasa, a school girl investigator who is good at disguise.
