expression, adverb
cheerfully; happily; in good humor
Describes doing something in a cheerful, willing, or good-natured manner. Often used when someone acts without complaint or with a pleasant attitude.
彼は機嫌よく手伝ってくれた。
He cheerfully helped me.
機嫌よく歌を歌っている。
She is singing happily.
Formed from the noun 機嫌 (mood, temper) and the adverbial form of 良い (よい), meaning 'in a good mood' or 'cheerfully'.