Kimetsu Gakuen: Valentine-hen

キメツ学園 バレンタイン編

Zenitsu Agatsuma is determined to be the subject of adoration by receiving chocolates on Valentine’s Day—and this year, he is taking no chances. Enlisting the help of his friend Tanjirou Kamado, the two are prepared to learn from some of Kimetsu Academy's most popular figures. Together, they ask Kyoujurou Rengoku, the history teacher; Giyuu Tomioka, the PE teacher; and Tengen Uzui, the art teacher, about the secrets to their popularity. However, only time will tell if following their advice will bring the same success for Zenitsu.

(Source: MAL Rewrite)

Note: Related to the post-credit shorts after episodes 14, 17 on the TV broadcast of Kimetsu no Yaiba.