Holy shiit it's Estio. I am 20 and I remember having hated this 4 years ago, when I first started reading it. I know that I've read worse, but I specifically remember this as being one of my least favourite ones, despite me having read this for quite a while. Really, there are 2 manhwas that I vividly remember for dropping as the quality deteriorated. Estio is one and then there is another one with a female main character and some polymorphing black puma or smth. But Estio is most certainly the worse of the 2.