yuri and yoona were playmates since young they were like peanut butter and jelly yuri comes from a single parent family and yoona in the  other hand came from a wealty family   she was yuri's pillar of support 

yuri 

yuri is a girl that comes from a single parent  she grew up in seoul her mum divourced her father due to gamling inssues 

yoona 

yoona is yuri's playmate since after a  few years later yoona developed a strange feeling for yuri what could that feeling be ?

superjunior

superjunior  is a gang formed by 13 guys they back yuri and yoona up eventhough they are not part of the gang as their parents object to it 

DBSK

DBSK is superjunior's sunbae they are the closes to superjunior  since they are superjunior's friends they are also yuri and yoona's friends  

no minwoo

minwoo is yuri's younger brother the reason why minwoo has a diffrent surname as yuri is because minwoo is adopted yuri's dad has never liked minwoo since childhood so minwoo had no choice but to move out