Щелкунчик Китаро (2018)

Nearly twenty years into the 21st century, people have forgotten the existence of youkai. 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 Youkai Post in search of answers, only to be greeted by Gegege no Kitarou... (Source: Crunchyroll)