Maryoku Zero de Mezametara, Saikyou Mahoutsukai-sama (Moto Yashinaigo) ga Rippa na Yandere ni NatteimashitaNew魔力0で目覚めたら、最強魔法使い様（元養い子）が立派なヤンデレになっていました; When I Woke Up with Zero Magic Power, the Strongest Mage (My Former Foster Child) Had Become a Perfect Yandere

Erika, a saint, used a forbidden spell to save the life of Cain, an orphan boy she had raised at the orphanage. The magic should have cost Erika her own life. Instead, she awakens to find an unfamiliar man at her bedside. He tells her that he is Cain, the very foster child she once saved. Twenty years have passed since that day, and Erika has been asleep the entire time. In the years she lost, Cain grew up and rose to become a duke and the foremost mage in the land. Unwilling to burden him any further, Erika tries to leave his side. But Cain will not allow it. "You were going to leave without telling me?" he asks, and she begins to learn the depth of the obsessive love he has harbored for twenty years. His kisses are so deep and heated that she has nowhere to escape. The mere touch of his clinging hands makes her supposedly innocent body ache with sweet longing. Unable to understand her own reactions, Erika is swept up in a devotion that has waited two decades to claim her.