Danshi da to Omotteita Osananajimi to no Shinkon Seikatsu ga Umakuiki sugiru Kudan ni Tsuite

Danshi da to Omotteita Osananajimi to no Shinkon Seikatsu ga Umakuiki sugiru Kudan ni Tsuite summary:

Shuichi, a high school student, ended up marrying his childhood friend whom he thought was a boy. At their reunion after 10 years, his childhood friend Yuika had transformed into a beautiful girl, which initially made Shuichi quite nervous. However, as time passed, he gradually grew accustomed to the sense of closeness as best friends—
and thus, their love story as an ideal couple with a charming touch of innocence begins!