Genma Tonbo in Onimusha 3: Demon Siege.
The Genma Tonbo or just Tonbogiri (蜻蛉切 Dragonfly Cutter) is Heihachi's weapon of choice when you play the mini game unlocked at the end of the game. This weapon also appears in Onimusha: Dawn of Dreams as one of the weapons usable by Samanosuke Akechi.
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Genma Tonbo in Dawn of Dreams