WAGNARIA!!

Set in a family restaurant in Hokkaido, the northern prefecture of Japan, 16-year-old high school student Souta Takanashi works part-time along with his strange co-workers: Popura Taneshima, a high school girl who's a year older than Souta, yet easily mistaken for an elementary/middle schooler, and Kyoko Shirafuji, the 28-year-old store manager who doesn't bother to do any work at all. (Source: NIS America) — Description from AniList community (anilist.co).