The characters you actually care about suddenly act like real people instead of plot devices, cracking jokes that land because they know exactly who these people are. Four minutes is perfect because the pacing never lets a gag die, the chibi art sells every punchline, and by the time you blink it's over. This isn't a spinoff that apologizes for existing, it's fan service that gets what fans actually want.

Valentine's Day is coming at Kimetsu Academy, and Zenitsu Agatsuma is set on being showered with chocolates this year, leaving nothing to chance. He recruits his friend Tanjiro Kamado, and the pair go looking for tips from the school's most admired faculty: history teacher Kyojuro Rengoku, PE teacher Giyu Tomioka and art teacher Tengen Uzui. Each is asked what makes him so popular, and whether their advice will pay off for Zenitsu remains to be seen. This four-episode comedy ONA is a Valentine's special spun off from Kimetsu no Yaiba, connected to the post-credit shorts that followed episodes 14 and 17 of the TV broadcast.