Deer Nushi
The Deer Nushi is one of the confirmed Nushi bosses in Beast of Reincarnation. It is an early encounter on Emma's journey toward the Capital, and it serves as one of the game's first real progression gates.
When It Appears
The Deer Nushi fight is positioned early enough that Emma is still in the opening stretch of her arc. Previewed gameplay footage shows her going into the fight with only one flower in her hair, the original shakuyaku from Koo's resurrection scene.
Rewards
Clearing the Deer Nushi grants Emma a Sakura flower, which appears in her hair after the fight. Sakura joins the shakuyaku from the story's opening as part of the visible, flower-tracked Flower System that marks Emma's progression. Footage of the fight has shown purple-like tendrils covering both Emma and Koo in the aftermath, consistent with the way Blight corruption manifests when a new flower is gained.