koto-koto
The quiet, soothing sound of something simmering on low heat — a pot of stew cooking slowly, or a gentle knocking.
💡Making homemade soup — 'The stew was simmering koto-koto on the stove.'
鍋がことこと煮えている。
The pot is simmering koto-koto.
The soup was ___ simmering gently on the stove all afternoon.
スープが午後ずっとコンロで○○煮えていた。