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

The story is about a man, Shuichi, who marries his childhood friend and best friend, Yuika Karasuma. Shuichi, who attends a prestigious private school, is fed up with people who approach him only because of his family background. The story begins when he receives a proposal for an arranged marriage. (Source: Natalie, translated) Note: An extra chapter is included