TsuguKaji-Koto are Ai Kajigano (17 stringed koto and vocals) and Tsugumi Yamamoto (17 and 25 stringed koto/vocals). It's unusual for koto players to sing, but they seem to pull it off quite well.
1. Pattern 2. Yukionna 3. Ehon no Naka kara 4.Istumo Mieru Kawa 5. Hoshi ni natta Otoko 6. Mudai - Istuki no Komoriuta