|Japanese premiere||December 16, 2017|
Yo-kai Watch Shadowside: The Return of the Oni King (Japanese: 映画 妖怪ウォッチ シャドウサイド 鬼王の復活 Eiga Yōkai Wotchi: Shadousaido Oni-ō no fukkatsu) is the fourth theatrical film in the Yo-kai Watch franchise. It is about to debut in Japan on December 16, 2017.
"There used to be a boy who could control Yo-kai with a mysterious watch. However, he became unable to see Yo-kai when he became an adult. With the boy's duties finished, the watch was buried away in space-time. Then 30 years later, quiet everyday life comes to an end as a fateful day beging with a comey drawing near. The terrible Yo-kai virus Onimaro infects people's malevolent intentions and spreads infinitely. The one chosen by the Yo-kai Watch is the one who can save humanity from its crisis. The bond between humans and Yo-kai may be recovered with the attainment of a new Yo-kai Watch."
The movie was first revealed by the staff behind Yo-kai Watch the Movie: The Great Adventure of the Flying Whale & the Double World, Nyan!. They've stated that the fourth movie will be released during the winter of 2017 and that they would reveal its release date and its title on a later date.
In July, 2017, the title and its release date has been revealed in CoroCoro Comic which features Lightside and Shadowside transformations. It is revealed that Yo-kai will have the ability to transform into "lightside" and "shadowside" forms. In these forms, Yo-kai show different personalities, abilities, and appearances. The magazine shows pictures of Jibanyan, Komasan, and Whisper in lightside and shadowside forms.
The key to the story will be three new human characters, each of which may hold a Yo-kai watch of their own. The first character is Akinori, a boy who can see Yo-kai whose family manages a shrine. The second character is Natsume, a lively middle-school girl who is friends with Yo-kai. The third character is Tōma, a boy with a mysterious air that attracts Yo-kai.
More information about the three key characters has been revealed on the movie's official website. Natsume is a 13-year-old girl who nearly drowned in a river when she was very young. The girl who likes to take care of others remembers "something" saving her from drowning. Tōma is a 13-year-old boy whose parents are busy with work, so he is always alone. Akinori is the oldest son in a family that has used Yo-kai in fortune-telling for generations.