Gegege no Kitarou (2018)

Nearly twenty years into the 21st century, people have forgotten the existence of Yokai. When a number of unexplainable phenomena plague adults of the human world with confusion and chaos, thirteen-year-old Mana writes a letter to the Yokai Post in search of answers, only to be greeted by Ge Ge Ge no Kitaro...

(Source: Crunchyroll)