Fourth Period: Spinning Time

A week after joining, Itona is assembling a high-tech remote-control armored car, and the boys marvel at the talent his tentacles had once dulled, though his sharp tongue remains. He shares a crucial detail about Korosensei, whose heart sits just beneath the crescent-moon tie, a weakness the teacher expects to become common knowledge. During a test drive toward the staff room, the camera catches some of the girls, and the group instantly fixates on peeking under skirts, brainstorming upgrades to the machine's stealth and lenses. Only Nagisa and Isogai hesitate, recalling how angry the class had been over the earlier underwear thefts.

The improved model is wrecked by an angry weasel the next morning, yet Itona pledges to keep refining it. Okajima's loud vow to spy on every girl is overheard, and Ritsu's ill-timed announcement of a completed fish-eye camera confirms their suspicions. Left to face the fallout alone, Okajima watches Itona slip off to skip class with Karma.

Later, Kayano unpacks the meaning of Itona's name as becoming a thread, and he fires back that plenty of classmates have odd names. That spurs a run of name talk: Kimura's given name means Justice, saddled on him by police-officer parents devoted to law and order, while Hazama feels she can never match hers. Karma, by contrast, likes his own. Yada proposes assigning everyone a code name for the day like the island assassins, with picks drawn from a lottery box, and Korosensei bans real names outright.

By PE the students are glum about their labels. Kimura alone keeps his full name, since Korosensei reasons the word Justice would land well with the public if Kimura made the kill. The teacher argues that deeds define a person more than a birth name, and after the class rejects his grandiose suggestion he ends up dubbed a ridiculous string of insults, which they admit is funny. Kayano demands to know who tagged her Forever Flat as Muramatsu quietly flees. Meanwhile, chairman Gakuho Asano and his son Gakushu discuss Class E's troubling rise, with Gakushu vowing to handle them before mid-terms.

The fourth season-two episode adapts chapters 88 and 89. In manga differences, Korosensei reviewing Itona's grades and Karasuma questioning his intelligence are cut, the anime uniquely blames Okajima for everything, and it shows Itona skipping class with Karma rather than quietly avoiding the scolding. It aired in Japan on January 28, 2016, with the dub on March 2, 2016.