Not a friend, but an 'enemy'

Yoongi: Same age Same class 4, first year at BTS High School as Yeoju and Jimin Jimin: Same age Same class 3, third year at middle school as Yeoju Same class 4, first year at BTS High School as Yeoju and Yoongi Jungkook: Yeoju's younger brother, two years younger than him Seokjin: Homeroom teacher for class 4, first year (Korean)