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

Shuichi Konoe is going to marry Yuika Karasuma, a childhood friend who he thought was a boy when they were younger. Their newlywed life is like being best friends, with a familiar and comfortable sense of distance between them. But both of them are starting to feel conscious of each other as something more!?

(Source: Sneaker Bunko, translated)