Every harem has a first member, the one the protagonist loves the most, the one who supports him mentally, the one who will never abandon him even if the whole world is his enemy, and the one who ends up sharing the mc.
But what would happen if that person became a villain?
Just to tell you to read up to chapter 20.
I think after those chapters this story becomes entertaining.
Give it a chance.
But if you drop it please do a review so I can do better.
PD: The picture is not my image if the author is annoyed with its use then please let me know.