He is the main antagonist in Yo-kai Watch Shadowside: Return of the Oni King.
- Yo-kai Watch Shadowside: Return of the Oni King: Antagonist
- Yo-kai Watch: Wibble Wobble: Playable Yo-kai
- Yo-kai Watch Shadowside: Minor Yo-kai
Onion Rasen is a silver overweight oni with grey armor.
In his De-Armored form, he loses a few pounds. His speed has also significantly increased.
In his Fragment form, he resembles a four-armed shadowy figure.
Yo-kai Watch Shadowside: Return of the Oni King
Yo-kai Watch: Wibble Wobble
His name translates into Oni King Rasen (Japanese: 鬼王・羅仙 Oniō Rasen).
- When he gets beheaded by Touma, he manages to stab Touma with a fragment of his blood, which is a reference to Shuten doji from Japanese mythology.
- A fragment of his which appeared in SS022 went by the name of Kabila.