The young boy Felix, who admires the Kingdom's Knights, is suddenly on a certain day set up as the Kingdom's crown prince, unanticipating that he would live a life immersed in sex. There is a queen who is also a mother, there are maids, and an ex-boss female knight, but other cougars approach! The innocent boy's reasoning is on the brink of destruction.

With over 50 books at this point, the Harem Series is by far the longest 18+ LN series out there. Most of the novels aren't directly connected, but they all take place in the same fantasy world.

For now, let's take a look at very first entry in the series: Harem Castle (ハーレムキャッスル).