I probably read this series through Kindle Unlimited.
A young man wakes up and discovers that he is in an alternative world with magic. He also has magic powers himself. Fairly soon, he arrives at a town where he enters and wins a contest/tournament (either archery or throwing knives, I can’t recall), and is given land, money, the King's daughter's hand in marriage (total wish-fulfillment, I know).
The land in question is under attack by miscellaneous monsters. Eventually he marries the daughter and her two sisters, and they start a school to teach magic (exclusively to women). He constantly denies that it is a harem.
Eventually, he annoys the king and goes on a homesteading trip.