Tragedy of Yosuga Pass

Ten years prior the start of the series, three shinobi from Kirigakure, Ganryū, Suiren and Junsai were sent on a mission to retrieve a document taken by Kumogakure with Iwagakure's assistance. However, when the document was retrieved, the Iwa shinobi sent betrayed the Kiri team and killed Junsai and Suiren, who sacrificed herself to save Ganryū. Since that day, Ganryū has held a deep hatred against Iwa.