How can juniors likes a senior? It will comes out sweetly or miserable?

Seohyun, a senior in Dongguk University, a smart and beautiful girl. Had a lot of admirer, almost all of them was her juniors but she never dated one. Her mindset "never dated someone that younger than her" her friends always told her to forget this mindset and dated 1 of them, almost all of her friends were dating juniors, but she just can't. Until one day, 2 juniors capture her heart.

Jeon Jungkook, a freshmen in Dongguk University. A handsome and naughty boy, he has a gang named BTS but the other members were his seniors. Playing around with many girls but nobody really capture his heart. Until one day he met Seo Joohyun, his seniors. He was falls hard for her. But there is someone likes Seo Joohyun too and he was Kim Taehyung, his bestfriend in one gang.

Kim Taehyung, same with Jeon Jungkook a freshmen. A handsome, smart and naughty boy, in a gang called BTS too. He was the one that had a lot of common with Jeon Jungkook. Falling in love with Seo Joohyun when he first saw her. Became love rival with Jeon Jungkook but in a peace/ good way.

Who will Seo Joohyun choose?
Or she'll be still on her mindset?