Mizu shika Denai Shingu [Cup] wo Sazukatta Boku wa, Fumou no Ryouchi de Suki ni Ikiru koto ni Shimashita

Since Sian is a young man born into a wealthy aristocratic family, you would think that his life would be easy. However, the sole gift he receives at his coming-of-age ceremony—where he is given magical power—is a seemingly useless "cup" that merely causes water to pour out of it. As a result, Sian is declared a worthless dunce and banished to live as a fictitious medieval ruler in a distant desert. Even after reaching the lowest point, Sian remains determined to bring life back to the desolate area. The dried-up oasis is restored by him using the water poured from his "cup" and he begins to make the locals smile again. At that point, his "cup" comes back to life and is revealed to be the Holy Grail. Using his "cup" to the fullest, Sian challenges himself by growing magical plants, creating a city the way he wants it, and creating regional specialties to market!