Sakuya is the Stage 5 Boss in Embodiment of Scarlet Devil, and subsequently one of the main protagonists of the Touhou series in later games. A mysterious maid working for her mistress Remilia in the Scarlet Devil Mansion, she mainly fights by throwing knives and other bladed objects at people and using her time manipulating powers to freeze time.
Gameplay Tips
Sakuya's Up Special has a counter at the start when used on the ground. It hits from any range and activates from projectiles, making it a good option against zoners.
During timestop, Sakuya can setup knife projectiles or just hit the opponent with attacks. Hitting them does more damage, but using projectiles looks cooler.
Sakuya's Side Special can be charged. At full charge, it's a very strong projectile. It can also be aimed downwards in mid-air.
Trivia
Sakuya's voicelines come from Koumajou Densetsu 2. Her VA is Miyuki Sawashiro, who voiced characters like Cammy from Street Fighter and Elizabeth from Persona 3.