Short: Part thriller, Part fluffy romance. Both excellent. It's got happy bits, funny bits, sad bits, and it's got warm messages throughout. The thriller element works well and is absolutely equal partners with other aspects of the story. Really enjoyed!

Detail:
Picked this one up because it's got Gong Hyo Jin - I've always liked her style and the characters she plays. It's introduced me to Kang Ha Neul though who as the ML was excellent with a wide range in his character from the goofy to the dead serious and it all fit perfectly.

The story features a really good thriller element that literally right from the opening scene will have you puzzling, the story will misdirect, and also present you with straight facts, and you'll need to figure out what's right and what's misdirection, who did it? who's going to do it? I did wonder whether the thriller element might be weak in comparison to the usual romance elements but it gets equal footing in the story and is constantly there being worked on and developed throughout the story. The way it lays out motive for numerous people to take an action over the course of many episodes was really nicely done.

A key element of this story is about mothers, about the FL's mother, about the FL who is herself a mother, about the ML's mother, and about other mothers in the neighborhood, about the mother of the boys father, there's an overarching element in this story about the strength and power of mothers everywhere. I did find that, as a father, the story seemed a bit negative towards fathers - with abusive, ignorant, idle, absent, drunk fathers being pretty much the mainstay of the story but... i'm gonna let that pass because I know some single mums and i'm in constant awe of them, they should be celebrated. The message here is a good one. I particularly liked a quote in the story 'Mums exist because God can't be everywhere", how nice is that?

The romance is nicely done, with the FL showing exactly zero interest in the ML for a while and him goofing around and hanging around her all the time winding her up before things begin to progress. It does have the usual KDrama break-up but it's valid, not stupid, and in fact amusingly at one point the FL's mother does comment that she hates in tv shows when they say they're "breaking up because they love you" and how stupid it is :)

It has a light love triangle, but barely and not enough to annoy those who are turned off by them.

A great story, which keeps you guessing, gets you interested in the characters, rooting for their successes and feeling pains at their losses.

Nice music too, not listened to the OST separately but a few I was humming along to, which is a sign there'll be some nice tracks to listen to there I think.

Definitely recommended, the blend of the thriller and the romance makes it a bit different to the usual.