Misao no Keiyaku, also known as 操の契約, is a Japanese manga by author Yuki Shiraishi that blends supernatural suspense with psychological romance. The story takes place in contemporary Japan, centering on a mysterious and ancient binding ritual known as the "Contract of Misao." This pact is not a simple verbal promise but a spiritual and physical bond that ties two individuals together through blood, fate, and the exchange of life force. The contract is usually enacted between a human and a non-human entity, often a yokai or a spirit, and it demands absolute obedience from the human signatory.

The main protagonist is Misao Tachibana, a high school girl who has lived a quiet and unremarkable life until she inadvertently becomes entangled in her family’s hidden legacy. Her grandmother, a shrine maiden, had once sealed a powerful and volatile spirit named Kei, who takes the form of a handsome young man with fox-like features and a capricious nature. When Misao accidentally breaks the seal while cleaning the family shrine, Kei is freed and immediately claims her as his new contractor. However, the contract is not one of servitude for Kei; instead, Misao is bound to Kei as his "master" in name, but the power dynamic is dangerously reversed. Kei requires Misao's life energy to maintain his physical form, and in return, he grants her supernatural protection. But the contract has a cruel clause: every time Misao uses Kei’s power, her own lifespan is shortened, and she slowly loses her emotional memories, making her increasingly reliant on him.

The primary conflict arises from Misao’s struggle to maintain her identity and humanity while being drawn deeper into Kei’s world of spirits, cursed artifacts, and rogue yokai. Kei himself is not wholly malevolent, but he is driven by his own tragic past—he was once a human who was transformed into a spirit and betrayed by his previous contractor, which left him bitter and untrusting. As Misao and Kei navigate their strained partnership, they encounter other contract holders, each with their own tragic stories and twisted pacts. The narrative arc follows Misao's gradual discovery that the contract can be rewritten or broken, but only if both parties willingly sacrifice something irreplaceable. A major subplot involves a rival spirit hunter clan that views all contracts as abominations and seeks to exterminate both Kei and Misao, forcing them into uneasy alliances.

Notable narrative arcs include the "Memory Thief Arc," where Misao loses a crucial childhood memory after saving a classmate, prompting Kei to reluctantly assist her in tracking down a yokai that feeds on forgotten moments. In the "Betrayer's Pact Arc," a former contractor of Kei resurfaces, manipulating Misao into believing that Kei is secretly plotting to consume her entirely, which tests their fragile trust. The "Seal Breaking Arc" reveals that Misao’s grandmother intentionally left the seal weak, hoping Misao would inherit the contract to protect the town from a greater evil—a shadow entity that absorbs other spirits. The story culminates in a choice between breaking the contract and losing Kei forever, or fulfilling it fully and surrendering her remaining memories, making her a hollow vessel for his power. Throughout, the manga explores themes of consent, memory, identity, and whether a bond formed under coercion can evolve into genuine affection.