|This article is about a/an character in Kamen Rider Build.|
Following his director Gentoku Himuro, Matsui was part of a cabal of scientists of the Touto Institute of Advanced Matter Physics who sought to continue Takumi Katsuragi's officially suspended research into Nebula Gas in 2015. Alongside Yoshikazu Takahashi, Matsui introduced himself to Katsuragi as his assistants. When Gentoku named the group Faust, Matsui was among the personnel who cheered him on.
- "Gear Engine! Funky! (Rock music, engine revving) Engine Running Gear!"
- ―Transformation announcement[src]
- Height: 203.0 cm.
- Weight: 103.5 kg.
- Punching Power: 30.2 t.
- Kicking Power: 37.2 t.
- Maximum Jump Height: 48.6 m.
- Maximum Running Speed: 100 m. per 1.7 sec.
One half of the Hell Bro's, Engine Bro's (エンジンブロス Enjin Burosu) is the white Kaiser, transformed into by inserting the Gear Engine into the Nebulasteam Gun. This updated Kaiser System was created by Nariaki Utsumi, based on that originally developed by Kaisei Mogami.