Lonely Attack on the Different World (WN) - Chapter 261

As a wandering soul trapped in endless cycles of reincarnations, Claus must decide what to do in his current life.

Wang Bo was fed up with his job being a programmer, especially because of all of the nights he was working overtime without pay. His boss had given him a mysterious game to beta test in his free time, which had granted him possession of unclaimed territory in New Zealand with which to improve to his desires. After a certain event in his company, he ended up quitting his job. His lack of goals and curiosity eventually led him to buy a ticket to New Zealand, in order to see if the unclaimed territory given to him in the game was actually real. Watch, as he develops this beautiful, fertile stretch of land into prosperity, by building villages, farms, schools, hospitals and more.

- Description from Novelupdates

When I became a rich young master, I had to enjoy it.

The second prince has come of age. To celebrate the advent of such an occasion, the search for a suitable bride began. My younger sister was expected to go to the Royal Palace as a candidate. However, despite this, she eloped the day before her departure. I, the older sister she left behind, looked almost exactly like her – so much that we were often mistaken for twins…

One month, right? For just one month, shall I substitute in for my sister?