Flower Thief is Matenro
The second semester has begun. However, Hiroshi and Susumu had not finished their summer homework. So Ochiai-sensei orders him to stay up all night tonight and finish his homework. And that night. Matenro is seen at Hiroshi's classmate Mamoru's house. Matenro let Mamoru's pet owl escape and stole Hinausu Yukisou...!