3-E student Isogai breaks the school rules by working part-time to help support his family. When Gakushu and rest of the Big Four students find out, they use his secret as leverage to force 3-E to participate in a bizarre sports-day competition. Soon it's time for the school's midterm competition as well, but when some 3-E students accidentally injure the elderly owner of a day care/after-school program, Koro Sensei forbids them from studying and orders them to replace him until he recovers! Assassination is one thing, but babysitting little kids...?! And then, our friends rescue a cat.