embers; dying fire; remaining fire
Refers to the glowing remains of a fire after the flames have died down. Often used in literary or poetic contexts to evoke a fading warmth or lingering passion.
キャンプファイヤーの残り火がまだ赤く光っていた。
The embers of the campfire were still glowing red.
彼は暖炉の残り火を見つめながら物思いにふけった。
He stared at the dying embers in the fireplace, lost in thought.
Compound of 残り (nokori, 'remaining') + 火 (hi, 'fire'), with rendaku voicing of 火 to び.