Sakura, operating under the alias Sacrament, serves as a pivotal and enigmatic force within the narrative. She possesses distinctive physical traits: knee-length pink hair featuring a single ahoge (hair antenna), secured by a yellow headband, and pale purple eyes.

Her first appearance unfolds aboard the Premium Ambriel, where she engages Souta Hatate in a strategic chess-like match. Following his defeat, she grants him the unique ability to perceive and manipulate "flags" signifying potential futures. This power transfer comes with a directive: Souta must uncover the fundamental truth of their world. She imposes the condition that upon achieving this goal, they will battle once more.

Later, Sakura intervenes again, targeting Mei Daimyouzamurai. She swiftly revokes Mei's flag-observing abilities and excises the associated memories. She justifies this action by asserting that Souta must discover the world's truth without such aid. This intervention underscores her function as a guardian of knowledge and a catalyst solely for Souta's journey.

Her name, Sakura (桜), translates to "cherry blossom," carrying inherent symbolism.