Koikuchi Shoyu (Dark Soy Sauce) (濃口醤油)
The standard Japanese soy sauce - equal parts soybean and wheat, used for both cooking and the table across most of Japan.
| JAS type | Koikuchi ('dark mouth') - the most produced type in Japan, the great majority of domestic output |
|---|---|
| Ingredients | Soybeans and wheat in roughly equal amounts |
| Use | All-purpose: cooking, dipping, seasoning |
When a Japanese recipe just says 'soy sauce', it means koikuchi. Its balance - salt, savoury depth, a little sweetness and aroma - is the reference flavour the other four types are compared against.
Abroad, koikuchi is the default bottle to own: major export brands' standard products are koikuchi. Regional koikuchi styles exist (Kanto's is the national reference; Kyushu's tends sweeter), but the type name on the label is the reliable guide.
See also
Choosing in one tableRelated page in this guide.Usukuchi
Related page in this guide.
Sources: Ministry of Agriculture, Forestry and Fisheries (MAFF), 'Traditional Foods in Japan'; JAS soy sauce standards; Umami Information Center; Kikkoman official information; Wikipedia (CC BY-SA 4.0). Checked 6 November 2026.