Ranma ½ (1989)

S1E55 Back to the Happosai!

A mystical mirror transports Ranma and his friends several centuries into the past, landing them in a quaint Chinese village. There, they encounter a young Cologne, who finds herself conflicted by her feelings towards an 18-year-old adventurer named Happy, notorious for his underwear thievery. As she grapples with her emotions of attraction and repulsion, the group must navigate the complexities of this unexpected time travel while dealing with the antics of the mischievous Happy.