Karin wood is used to for low-end shamisen. It is softer and more widely available than the following woods, so shamisen makers use this to build affordable models. The downside of a Karin sao is it may warp and wear more than heavier woods below.
Note All dou are made from Karin wood of varying grades, depending on the quality of shamisen. E.g, cheaper shamisen uses low-grade Karin. Good wood, but without fancy grain patterns. Expensive shamisen uses very high grade Karin which is harder and has luscious grain patterns.
