It is first mentioned by Kyuemon Izayoi when he confronts Yoshitaka. During his battle with Gengetsu Kibaoni, he supposedly had the power to permanently seal him with the End Shuriken, but instead used the 48 Sealing Shuriken to imprison him temporarily before he would revive years later. Kyuemon demands Yoshitaka hands over the End Shuriken, while he initially refuses to acknowledge he has such a thing. During their fight, Kyuemon deduces that he couldn't seal Kibaoni permanently because he wasn't strong enough to use the End Shuriken, only for Yoshitaka to tell her that he chose not to. Shinobi 6: Tengu's Spiriting Away