Kanroni is one of boiled and seasoned dishes. It is also called ameni (literally, candy cooking).
After broiling mainly freshwater fish such as ayu (sweetfish), carps, gobies, crucian carps, and lake smelts without seasoning or as raw, simmer them in the soup with soy sauce, mirin (sweet cooking rice wine), and plenty of sugar and mizuame (starch syrup) to have 'teri' (glaze).
Simmer them slowly for a long time until the bones become soft and add mizuame last to have teri again.
It turns out just right with small fish than big one.
It is also called kanroni that fruits like chestnuts and Chinese oranges are boiled with sugar.