SHUSUI

'Shusui' is the term applied to the doitsu version of Asagi. The term 'shusui' translates to 'autumn water.'
Just like an asagi, the top half of the body of a shusui is also light bluish in color, while its undersides exhibit red or orange markings. Being a doitsu though, the shusui can not exhibit a netting effect like an asagi, since it has no scales to show reticulation. Instead, an important feature of a shusui is its line of mirror scales running along its spine from the back of the head to its tail.

'Hi Shusui' refers to a shusui koi whose blue body is almost completely covered with red coloration. A hi shusui that exhibits blue mirror scales on both lateral lines is known as 'hana shusui.'

Appreciation Criteria
Color
The Shusui's body must be blue in color above the lateral line. The blue color must be of even shade and hue within a single koi, although it may vary from one koi to another.
Aside from the blue color of the shusui above its lateral line, it must have red coloration on the underside of the its body, just below the lateral line. This red color may also appear on all fins, the gill covers, and mouth.
Pattern
The mirror scales of a shusui along its back must be in a straight row with no gaps in between from the back of the head to its tail. The head of a shusui must be clean, i.e., it must not exhibit any imperfections or small black spots.