The beginning of this drama is a little confusing, because there's a short opening scene in the present and then there's a long (!) flashback that lasts for more than half of the entire series. I recommend ignoring that and just focusing on the rest of the story, which luckily doesn't use flashbacks and flash-forwards as much as I feared.

The story itself is good, but nothing exceptional: a fated encounter between a member of a gang and a high-school student leads to them having to live together for a while and slowly develop feelings for each other. The plot also follows the story of two other members of the gang and the love triangle between them and their boss. I feel like the organized crime aspect of the plot should have been explored more, especially in terms of who is aligned with whom and what do these gangs actually do other than fighting each other whenever they meet.

The romance can be good or not, it all depends on personal taste: it feels like the love stories don't have solid foundations and they're mostly based on the ideas of "fate", "soulmates", and more in general the will to give up on anything for a lover. The main characters seem to share this extreme sentiment when it comes to love, so if that's too much for you, I can't recommend watching. I personally found it very romantic - maybe a little too idealistic to feel real, but it's also nice to dream every now and then, isn't it?
I believe that the couples featured in the drama are the best part. The acting is not stellar, but they deliver their performances very well and their chemistry was enough to glue my eyes to the screen.

I can't say that this story was great, or that I'd recommend this drama for its plot. On the other hand, I had fun and the couples are very sweet and memorable to me. I believe you should give it a chance if you like romance with a good amount of angst.