Life stages
Tosai, nisai, oya
Japanese keepers age ranchu by show season rather than birthday. The three names show up on every breeder's price list, so they are worth knowing.
当歳
Tosai
FIRST YEAR · 0–12 MONTHS
Hatched in spring, sold from summer. Body 2–4 in, little or no wen, color still changing. Cheap and plentiful, but you are buying potential, not a finished shape.
二歳
Nisai
SECOND YEAR · 12–24 MONTHS
The wen starts to fill in and the back shape becomes clear. The sweet spot for a hobbyist: still affordable, but you can see what the fish will be.
親
Oya
THIRD YEAR AND OLDER
Adult, full wen, full body. Breeding stock and show fish. Shape is fixed, so what you see is what you keep. Priced accordingly.