Danshi da to Omotte Ita Osananajimi to no Shinkon Seikatsu ga Umaku Ikisugiru Ken Nitsuite

When Shuichi was a child, he used to play with Yuu, a carefree boy who enjoyed exploring, roughhousing, and video games, and the two quickly became best friends. Now, ten years later, they’ve been reunited at an arranged marriage meeting, and it turns out that boy was actually a girl all along! What’s more, she’s become a beautiful young woman who wants him for a husband! It’s an awkward reunion, but can the two rekindle their friendship? And maybe let it become something more…?

(Source: Seven Seas Entertainment)

Note: Includes an extra chapter.