The black Ryu represents Evil Ryu, the darker form of Ryu overcome by the Satsui no Hadou who wears a black outfit.
The stage represents Suzaku Castle, a stage in the Street Fighter II series where Evil Ryu's debut game, Street Fighter Alpha 2 serves as its prequel.
The music track represents the musical theme of M. Bison's boss battle, referencing Evil Ryu's role as a villainous character who uses darkness-based powers in combat.
The Sudden Final Smash and Attack Power ↑ rules reference how Evil Ryu uses more a powerful version of the Ansatsuken fighting style than Ryu, empowered by the Satui no Hado.
Other trivia:
This spirit's Neutral type references how Ryu succumbs to the Satsui no Hado, transforming him into Evil Ryu.
This spirit's Fist Attack ↑ ability further references how Evil Ryu's Ansatsuken fighting style becomes more powerful when empowered by the Satsui no Hado.
