i am a sure fan of this drama, too. one of the best i've seen! fun, touching and moving story. we will really feel the emotions of the character here.
Se-Jin as an aspiring diplomat and a young mother who is secretly in love with her husband.
Seung-wan as an aspiring pilot and as a young father who is torn between his past love and his growing love for his wife.
Do-hyun as an aspiring pilot also but cant pursue it because of his eye problem and as a shoulder to cry on by Se-jin. He happens to fall for Se-jin but cannot say or show his feelings. a great friend.
actually i became more attach to Lee Ji-hoons character here, because he's so kind to Se-jin. he is always there for her.
i wisj LJH and Eugene will have their own drama next. they have a chemistry. aside from the fact that they have a real romance before, they are still very match for each other. im sure many will approve of this.

if you want to listen to the song What a Wonderful World. the fave song of Se-jin heres the link
http://www.minibite.com/oldies/wonworld.htmand the lyrics
I see trees of green, red roses too
I see them bloom for me and you
And I think to myself, what a wonderful world
I see skies of blue and clouds of white
The bright blessed day, the dark sacred night
And I think to myself, what a wonderful world
The colours of the rainbow, so pretty in the sky
Are also on the faces of people going by
I see friends shakin' hands, sayin' "How do you do?"
They're really saying "I love you"
I hear babies cryin', I watch them grow
They'll learn much more than I'll ever know
And I think to myself, what a wonderful world
Yes, I think to myself, what a wonderful world
Oh yeah