This trout lives in one lake and nowhere else. Its nearest relatives are fish that hatch in a river, go down to the sea and come back; this one stayed behind, and completes an entire life inside fresh water, in a basin ringed by mountains in Shiga. You can tell it apart by the eyes, which are larger than they ought to be.

Locally it is called ame-no-uo, the rain fish, because it moves upriver in numbers on days of heavy rain. Three or four years after hatching it returns to the stream it came from in order to spawn, in the autumn, and through October and November nobody is permitted to take it.

The season for eating it is early summer. In June and July the fat comes up in the flesh, and a cut surface is a pale rose colour that looks more like sea trout than like anything you expect to be pulled out of a lake. Freshwater fish are often awkward to eat raw, because of what lives in them. This one carries very little of that, and is served as sashimi without any argument about it. It is also grilled, smoked, simmered and fried, though those feel like things done to a surplus.

In 2025 it was formally described again, as a species of its own. Nothing about the fish itself changed. It has been swimming in the same water the entire time, and only the drawer its name is filed in has moved.