na-adjective, noun
malicious; scheming; black-hearted
Describes a person who appears kind or harmless but harbors ill intent or cunning plans.
彼は腹黒いやつだ。
He's a malicious guy.
あの笑顔の裏には腹黒な考えがある。
Behind that smile lies a scheming mind.
na-adjective, noun
Manga slang for someone whose cruelty is hidden behind a friendly facade.
そのキャラは腹黒で有名だ。
That character is famous for being sly and cruel.