If perfection was a Korean Drama, I am sure this one would make the cut.

Character Development: Every character involving the leads and supporting alike, will grow on you. Their individual stories morphing into a whole within an office scenario will almost compel the viewer to feel the laughter, shock and turmoil with/within each one of them.
The depth and character development hence, comes out exactly on point. Not too fast neither too gradual, just perfect.

Plot: There as such, wasn't a well defined plot in here, a theme rather. Of reconciliation, mutual admiration, acceptance layered with a veil of enigma, that were some past memories. Which lemme tell you the drama pulled off. Brilliantly.

Acting: What more can I say of the overwhelming "aura" that is of Park Seo Joon that hasn't been said already. The guy himself is a masterpiece (even when he's trying to be an obnoxious douchebag).
Park Min Young complimented him thoroughly and I was impressed.
Everyone else kept me entertained throughout.
But I'll give the credit where it's due, the child actors especially Moon Woo Jin did the finest job.
For me, the excellent portrayal of the childhood trauma was in all honesty, the highest point of the show.

Extra: The love triangle could have been avoided but I forgive them cause they didn't stretch it pointlessly for too long.
Unpopular opinion, the blooming romance between Gwi Nam and Ji Ah was more fun than that of the lead pair. I mean the duo had their own quirks and toe curling moments which I enjoyed from the get go.

In conclusion, if you're into rom-coms you really can't miss out on this one!