Young ayu, known as "chiayu," are sweetfish of the ayu species, typically measuring around 10 to 15 centimeters in length. They have delicate flesh with a light and refined taste. The peak season for chiayu is from spring to early summer when they are particularly fatty and delicious.

Chiayu can be used in a variety of dishes. Grilling with salt is a common method, allowing the natural flavor of the fish to be enjoyed. Tempura provides a crispy exterior and tender interior. Simmering in a sweet soy sauce (kanroni) enhances their umami flavor. They are also used in vinegar dishes and simmered preparations. Chiayu are often cooked whole, adding to the visual appeal of the dish.