Testable using the spirit veil in the hero sandbox, bring one friend or move the bot by punching him over and over until he is in the right position. The spirit veil needs to be blocking your vision of your target.
Compare this to Lash's 1 which is allowed to deal damage through spirit veils even if he can't see the target he is hitting, Yamato needs vision of her target or else Crimson Slash will miss a target it otherwise had the appropriate range and raycast to hit.
Compare this to Lash's 1 which is allowed to deal damage through spirit veils even if he can't see the target he is hitting, Yamato needs vision of her target or else Crimson Slash will miss a target it otherwise had the appropriate range and raycast to hit.