Headasteam (Japanese: 暴走マッタナ氏 Bōsō Mattana-shi) is a Boss Yo-kai which appears in Yo-kai Watch 2: Psychic Specters. He is fought in the Hexpress engine room.



Headasteam is a large Yo-kai whose body is mostly composed by his head, gray in color, with the mouth area colored red; sporting four large fangs inside the mouth. He has three eyes: a green eye in his front, and two uneven eyes resembling pressure meters, the left one being larger and more detailed -with scale-like markings rounding it-. He has comparatively shorter and smaller arms with gloved hands. He sports a driver's hat, alluding to his position in the Hexpress.

Headasteam appears to have a very short temper.

He has enough energy to keep the Hexpress running, being connected to the engine system.


In this boss battle, each blow Headasteam receives fills a two-fold red bar in the left side of the background and a blue bar in the right side of the background. Pinning the valves in said side causes each of the bars to fill faster.


In Yo-Kai Watch 2: Psychic Specters, during the quest “Getting to Gera Gera”, the player finds the culprit for the broken lever and hands it to him. Headasteam, thinking the player was responsible for breaking the handle, fights the player. After defeating him, he calms down and the red part of himself turns to a bluish-purple shade. He then explains to the player that he is prone to losing his temper.


  • "Boso" describes the following: "running wildly; reckless driving; runaway; rampage".
  • Headasteam is based on the idiom "a head of steam", which describes a situation in which a person or an activity starts to become very active or successful.
  • Chomino comes from "Chaud" (hot) and "Cheminot" (railroader).


In other languagers

Language Name Meaning
Flag of Japan Japanese 暴走マッタナ氏 Bōsō Mattana-shi
Flag of France French Chominot
Flag of Spain Spanish Expresso
Flag of Germany German Stresskessel
Flag of Italy Italian Vaporix
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