adverb
diligently; industriously; working hard
Describes working steadily and persistently, often with a sense of busy, repetitive effort. Mimetic word evoking the sound or image of continuous small movements.
彼は毎日せっせと働いている。
He works diligently every day.
子供たちはせっせとおもちゃを片付けた。
The children busily put away their toys.