This drama definitely made me feel thankful that I am an only child!

The title already warns the viewer about what kind of relationship to expect, but it was even worse than I thought. This is sibling rivalry, and jealousy, at it's most toxic. There are some sweet, & amusing, moments, but it's mainly a revenge drama. Those in the mood for comedy should know that Lee Cho in's story is a depressing one.

The reason to watch this is So Ji Sub. He's intense, heartbreaking, charming, and he thankfully likes to linger in the shower ; ) I had no interest in watching an extreme hospital drama, which this show basically is, but he grabbed my interest from the start. As Cho In, he goes through an intense emotional transformation, and the beauty of his performance is the complexity in it. When parts of this drama became a little too over the top for me, So Ji Sub would bring just as much excitement while keeping it grounded in his honest portrayal. From episode 1- 20 he reminded me why he is one of my favorites. But seriously, did they really have to shoot him in the head AGAIN? And that's just the beginning...

I would definitely rate So Ji Sub's acting as a 10, but I had mixed feelings about the rest of the cast.

Shin Hyun Joon as Lee Seon-Woo, plays a worthy evil rival. I blame writers for giving his character barely any room for sympathy, but his performance was strong. I think he occasionally relied too much on wild eyed-stares, which sometimes came across as overacting. Overall I'd still give his performance a 9. He has one scene in particular, with So Ji Sub, towards the end of the series, that was absolutely heartbreaking. Their relationship is the core of this show, so his ability to match So Ji Sub's intensity is a huge plus.

In general, the evil characters are written to be cartoonishly evil, so over acting can' t be blamed on the actors. The biggest victim of this is Kim Hae Sook, who's character only makes sense if she is a violent sociopath. The same goes for Baek Seung Hyun as Choi Chi Soo. Their performances do add to the suspense, but I found their actions too unbelievable, even for K-Drama. They definitely portray characters that you can hate completely, but they were also let off the hook too easily, and way too many times, for my taste.

Out of the supporting cast I loved Lee Cho In's bromance with Oh Kang Chul. They share a lot of great action moments together, and touching bonding scenes. I also love the cute relationship between Drs Kim Hyun Joo & Kim Jin Geun, which added some much needed light moments. The most underrated performance is definitely Jang Yong, who had some great acting moments using just his eyes & finger.

I had mixed emotions about Han Ji Min as Oh Young Ji. I liked her chemistry with So Ji Sub from the start, and that it walked a fine line between flirty, and almost platonic playfulness. Eventually I grew bored with her being wide-eyed, and naive. For a character who was supposed to be so street smart, defected from the North, and survived on her own, she seemed way too dumb. At the same time, her innocence was sometimes cute when she was the victim of Cho In's spontaneous charm, and a few of their romantic moments are worth rewatching. This is also the first time I've seen her have a first kiss scene that didn't completely suck. That must be the power of So Ji Sub! lol.

The most disappointing character to me was Chae Jung Ahn as Kim Seo Yeon. She hit all the emotional notes, and cried very well, but she bored me. This is surprising since, unlike many of the other character's, Kim Seo Yeon was actually written with some depth. Her opening "love" scenes with Cho In felt flat, and lacked any chemistry. Her moments with Seon-Woo were written to move me, but they didn't. He seemed more like her stalker than someone she actually cared about. The fact that I didn't like her character, made the whole love triangle/square storyline a lot less effective for me.

I'm still not sure about recommending this drama or not. As much as I have complained about the writing, I must say that both the direction, and the soundtrack, are great! Fans of suspense may want to check this out, because the excitement over the uncertainty of what will happen next is consistent from beginning to end. Fans of So Ji Sub should definitely watch this because it's imperfections are worth sitting through in order to watch him be awesome for 20 episodes. I admit that I was never bored, but If another actor was in So Ji Sub's place I probably would have dropped it early on. I also can't see myself watching this again, unless I'm in desperate need of a So Ji Sub fix.

Wait, have I mentioned that I really like So Ji Sub? ; p