Guren Ichinose is Lieutenant Colonel of the Japanese Imperial Demon Army, the leader of the Guren-tai, and head of the Vampire Extermination Unit's Moon Demon Company. Guarded and cunning, Guren wields the Mahiru-no-yo, a Black Demon Cursed Gear.

Full history (manga spoilers ahead).

Notes: I'm begging everyone to read Catastrophe at Sixteen and Resurrection at Nineteen. They are canon to this portrayal. I will usually default to prior to current events in the manga (for obvious reasons).