I was aware of it since the JP launch, but initially skipped out on it because yeah, I thought it was just horny (had mostly just seen Karin's L2D). I decided to give it a chance when the Global version released because I was deeply bored, and it turned out to both be way less horny than I expected (though still pretty horny) and have a genuinely well-written story and cast of characters. The developer interviews are particularly illuminating in this respect.
For reference, isakusan is the scenario director, whereas hwansang is the art director. This is isakusan's first major work, but hwansang is probably known for illustrating a lot of characters in Elsword.