Kappa once had a terrifying reputation for dragging people to their death underwater and devouring their organs. From the 1950s, however, they have increasingly been seen as cute and humorous characters.
— À lire sur www.nippon.com/en/japan-topics/b02505/kappa-the-terror-of-japan’s-rivers.html
you probably heard about Kappa with anime like this one
Kappa no Coo natsu yasumi but they were more frightening before