Slang intensifier used before adjectives or verbs to mean 'incredibly' or 'like hell'. Often carries a rough, emphatic tone.
I'm incredibly tired.
like a demon; like the devil; fiercely
Literal or figurative comparison to an oni (demon/ogre), describing a fierce, relentless, or inhuman manner. Can be used in both negative and positive contexts (e.g., working like a demon).
Work like a demon.
He's crazy strong.
鬼のような形相で追いかけてきた。
He came after me with a demonic look on his face.