The sword appeares as a single-edged long-sword (resembling a katana). It's deep red hilt has three diamond symbols on it. It's sheath also has wears same symbols to fit the sword's appearance. Ounotsumi's hand guard has a tilde shape.
Nashi stated that she took the sword from the palace two weeks before arriving in Yasai and since, she is seen carrying the sword. The sword was brought by Kuma after the second Chouri wars (probably some time before the assamble of the Goshibito). Also, Taka seems to have some kind of relation with the sword.
- Ounotsumi is the first ancient sword to be named in the series and second to appear (Hangetsu being first).
- The sword's hang guard has three different appearances - on the first chapter's cover it has a rounded cross shape, in the chapter itself it had its tilde appearance but it's much rounded than in later chapters.