As others have said, the start is quite slow, but it is certainly an incredible one. While at first seeming to be a nonsensical shounen fighting series, it's definitely shaping up to be more of an intense fantasy series with quite a bit of mythology to back it up.
It has been a slow start, but things are gradually becoming clearer at this point, and I find myself consistently amazed at the revelations given by each successive chapter. Don't be fooled by the seemingly cliche and overused premise. Lessa definitely takes it to a different level, and a lot of thought seems to have gone into its making.
Most definitely sticking around to see where else this webtoon will go. I'm sure it'll be worth the ride.
edit: OK, this series is legitimately great. I wrote this initial review back when Rano and Lessa just met, and since then Lessa has gotten progressively better and better and I've grown to adore all the characters. Lessa is an absolute cutie, Rano is a lovable idiot who I want to slap in the face but also hug at the same time, and Lucy is a super great badass who is able to make the best out of a shitty situation. And, god, is the art perfect or what? Especially the mythological bits are beautifully drawn. Seriously, even if you're not that interested in the plot, read it for the art: it's gorgeous.
Season 2 is great too. It also gets to things a lot faster, and more Lucy, so everyone wins!