Kang Hyun Se (Kim Jae Won) grew up without knowing his father. Due to the lack of fatherly love, he was recruited by a gang and became a third rate mobster. After his mother's death, he inherits a kindergarden, but he must go through a hundred days of training in order to get it, so he becomes an assistant teacher under a kindergarden teacher Yoo Mi Rae (Han Ji Min) and they develop romantic feelings for one another. However, the kindergarden property sits in the middle of an proposed amusement park development, called "Rainbow Park". Hyun Se's boss needs the money from the construction company so he is manipulating Hyun Se's hatred towards his father and threatens Hyun Se's father with the kindergarden Hyunseh has. Little does Hyun Se know that Choi Shi Wan (one of the managers who work for Hyunseh's father), who is the ex-boyfriend of Yoo Mi Rae, struck a dirty deal with Hyun Se's boss and is trying to outscore everyone.
01. ma ni ma ni song - Tree Bicycle
02. Beautiful Day - Jung Tae Woo
03. nae ma eum eh joo dan eul ggal go - Tree Bicycle
04. nae sarang eun - Boo Hwal
05. hwe sang - Kim Dong Wook
06. geu dae neun - LOVEHOLIC
07. yun ga (Hip Hop ver.) - Mic Pink (Song Bo Ram)
08. da shi ddeu neun tae yang - Yun Kyu Sung
09. gae goo jaeng ee - Tree Bicycle
10. nae ge sarang eun nuh moo ssuh - Mic Pink (Park Shi Nae)
11. yun ga (Ballad ver.) - Mic Pink (Park Shi Nae)
12. Beautiful Day (French Jazz Ver.)
13. Beautiful Day (Love Theme)
14. Beautiful Day (Happy Hour)
15. jo pok Theme
16. Main Theme (gi bbeum) - Marching Band
17. Main Theme (Jazz Ver.)
18. Main Theme (Cute Ver.)
19. Main Theme (Piano Ver.)