Gouman to Zenryou

Kakeru Nishizawa and Mami Sakaniwa meet through a dating app, and they soon decide to get married. After their engagement, Mami suddenly disappears. In trying to find her, Kakeru must confront a side of Mami's past that he might not have wanted to know.

(Source: Anime News Network, edited)

Note: Gouman to Zenryou is based on the novel of the same name by Mizuki Tsujimura.