Muji is a general name for single-color Nishikigoi that have no patterns on their bodies. Typical Muji varieties include the yellow-bodied Karashigoi, the bright red Aka-muji, the austere brown Chagoi, and the pure white Shiro-muji. Especially, it is not unusual to see Karashigoi, which are larger in size, exceeding one meter in length, and their performance at koi-shows is remarkable. Matsuba, whose scales are colored black one by one, is also belonged in Muji, and there are Aka-matsuba and Ki-matsuba.
In the Muji category, Koi that are evenly colored all the way to the tips of the pectoral fins and have a good body shape are highly valued.

JAS No.2021 Muji

Muji has no imprints across the body.

Aka-muji has no imprints and the whole body is red.

Akame-aka-muji is red in the pupil of the eye and has the appearance characteristics of Aka-muji.

Shiro-muji has no imprints and the whole body is white.

Akame-shiro-muji is red in the pupil of the eye and has the appearance characteristics of Shiro-muji.

Kigoi has no imprints and the whole body is yellow.

Akame-kigoi is red in the pupil of the eye and has the appearance characteristics of Kigoi.

Chagoi has no imprints and the whole body is brown.

Soragoi has no imprints and the whole body is pale blue gray.

Karashigoi has no imprints and the whole body is a mustard color.

Karasugoi has no imprints and the whole body is jet black. In some individuals, the tips of the pectoral fin is white.

Aka-matsuba has a red body, and has a pine cone-like pattern (“matsuba-mon”) on the entire back due to the arrangement of scales with black parts.

Ki-matsuba has a yellow body and a "matsuba-mon" on the entire back.