This page explains how to find the Sasa Kai shrine.
How to Find the Shrine
Go to the top of Gerudo Tower and talk to Kass the bard. He shows you a shrine platform on the ground below, and says to shoot an arrow at the sun when the shadow of the tower is covering the platform.
Float down to the platform and make a campfire and sit until noon. Then stand on the platform and get an arrow ready. When the shadow of the tower touches the platform, it will start to glow orange. This occurs at about 2:55PM. Shoot an arrow at the sun and the shrine will appear.
About the Shrine
This is a Modest Test of Strength shrine. The Guardian Scout wields a Guardian Sword+ and a Guardian Spear+. The chest in the shrine contains a Frostblade.