I will now briefly introduce all the characters . 

Shim Changmin : Age 20 , senior high school student 

Shim Changmin is a stubborn but a very intelligent guy . He is as handsome as his Yunho hyung . Changmin is a perfect son and a nice , lovable little brother . He can be a little evil sometimes but has a special soft spot for someone known as Kim Junsu . His junior at school . Something about Kim Junsu gives Changmin a tickling sensation in his stomach . Changmin really wants to be friends with Junsu but doesn't know how ? 

Changmin has someone in his life he loves more than himself . Mangdoongie is Changmin pet and the biggest source of happiness in his life . ( Mangdoongie has a important role here keke ) 

Kim Junsu : Age 18 , junior high school student 

The cutest 18 years old boy you will ever come across is Kim Junsu . A very bright and energetic person . He loves animals , so he works at a pet clinic/shop as a part time job along with his childhood friend Lee Hyukjae . He is friendly and can easily make new friends but something about his senior student Shim Changmin makes him feel nervous . He feels like his heart will explode if Changmin is somewhere near him . But he knows he shouldn't be feeling what he feels towards Changmin or else someone name Park Yoochun will be mad and will punish him and just the thought of it makes him terrified . 

Park Yoochun : Age 28 , a successful business man 

Park Yoochun is a famous , successful business man and a close friend of Jaejoong . He is the biggest player out there and has a very close relationship with Kim Junsu . 

YunJae : Shim Yunho - Age 30 , a successful lawyer . Shim/Kim Jaejoong - Age 29 , an art teacher 

Yunho is the elder son of the Shim family . A very responsible and caring person . All his life Yunho has always made his parents proud of him . He loves and adores Changmin endlessly . Yunho and Changmin are 10 years apart yet they get along very well . At the age of 27 , after becoming a successful lawyer Yunho got married to Kim Jaejoong . Their marriage was arranged by their parents . They introduced Yunho to Jaejoong and they were engaged for a few months . After falling in love and  understanding each other they both got married with their parents blessings . Jaejoong is a very sweet and super caring person . He loves to spoil his brother in law Changmin . Because of his fragile image Jaejoong gets along with his mother in law very well and she adores him too much . 

Lee Hyukjae : Age 18 , Junsu's childhood friend . Someone who has always been with Junsu in his ups and downs . 

Lee Donghae : Age 20 ,  Changmin's close friend , a clumsy boy with a very nice personality . 

Cho Kyuhyun : Age 20 , Changmin's close friend , he is very intelligent , straightforward and has a very sharp tongue .