Korosensei vs. Saiki Kusuo ~Showdown in Iruma~

Kusuo Saiki, a psychic, visits the Mitsui Outlet Park in Iruma for his monthly irumanju, a regional confection balancing sweet bean paste with dough flavored by Sayama tea. As he reaches for the last one on the shelf, a tentacle beats him to it, and he looks up to find a disguised Korosensei. In a fraction of a second the creature not only lifted the treat but even manicured the boy's nails out of apparent guilt, moving far too fast for Saiki to counter. Determined to reclaim it, Saiki swaps the manju in Korosensei's grip for a trading card of local actor David Ito, then teleports away to the Sakurayama Observatory.

Korosensei tracks him down within seconds, boasting about the short trip from the shop. He admires the observatory as the perfect spot to enjoy the sweet, praising the hills to the west and the shops spreading east and south, and muses that both psychics and strange creatures need a place to belong. Saiki briefly assumes the teacher genuinely loves Iruma, until a glance into his thoughts reveals he is fixated purely on the irumanju. Seeing himself in that, Saiki decides to split the confection between the two of them, and Korosensei marvels that the boy read him so precisely.

Saiki narrowly loses the last irumanju to Korosensei's blinding speed, then outmaneuvers it by replacing the treat with a celebrity trading card and teleporting off. Korosensei's pursuit lands him at the observatory in roughly three seconds, catching up despite Saiki's instant travel. Reading the teacher's single-minded craving through his powers, Saiki relents and shares the sweet, closing the contest with a truce rather than a winner.

This seven-page extra first appeared in the Autumn 2012 issue of Jump NEXT! and unites Assassination Classroom with the fellow Shonen Jump title The Disaster of Kusuo Saiki. Both creators, Yusei Matsui and Shuichi Aso, come from Iruma, which the story uses as its setting. On the cover, the character's name was rendered Koro Sensei in the magazine printing but changed to Koro Teacher when collected in volume 2.