I think It’s not that he has a problem with the harem. It’s more about his fear that he’ll eventually become unnecessary. He used to be one of the greatest warriors in his country, but after becoming the queen, he feels like one of his main duties is to serve the King in bed. However, they haven’t been able to consummate their relationship.
He feels repulsed by Shuraka not because Shuraka did anything wrong, but because Shuraka shows him nothing but pure love and admiration. Despite that love, the King still goes to his concubines when he and the queen fail to consummate their marriage, and that hurts him deeply.

I dont really get why he's that upset?? It seemed like before he was fine with bro having a harem before he arrived... maybe that only applied to women cause he can't have a baby himself? Guess he feels some type of way about another man being there... but it's so obvious bro was just there so Shuraka can learn how to pound Tei's ass properly. Whatever, hope the misunderstanding doesn't last 20+ chapters.