Having lost his parents in a car crash when he was five years old, Yuu drifts between the foster homes of uncaring, disdainful relatives, leading to a lonely existence where he hides his feelings to placate others and avoid getting kicked out.

As Chiyo's demonic presence overwhelms Yuu, his fear forces his thoughts to focus on his foremost desire: the warmth of a family member.

Yuu panics, shocked at Chiyo's non-monstrous appearance, but she reassures him that their contract was not a dream, and simply asks that he call her 'sis'.

[3] It was then moved online to the ComicWalker and Niconico Seiga websites in April 2019 after Dengeki G's Comic ceased publication after its May 2019 issue.

[18] As part of Anime News Network's Spring 2018 manga guide, Rebecca Silverman, Amy McNulty, and Lynzee Loveridge reviewed the first volume.