There are times in our youth that are awkward, messy, and unforgettable that stay with us forever. In the heart of adolescence, this is the story of first love. Mingyu has quietly loved his childhood friend, Jiwoo, for as long as he can remember. Every time she laughs, complains, or casually drifts closer, his feelings deepen slowly but surely. The problem? Jiwoo has always had a thing for a very specific type: big, muscular "beast-like" guys. That's the total opposite of Mingyu. Thankfully, she’s never seriously liked anyone in real life so Mingyu has stayed in his role as the dependable “guy friend,” standing loyally by her side. But one calm autumn day, his peaceful world is shattered. “Joo Mingyu… I think I’m in love.” Out of the blue, Jiwoo falls head over heels for Kang Taemin, the captain of the school volleyball team. Now faced with the terrifying possibility that this might be her first real love, Mingyu realizes: it’s do-or-die. Determined not to lose her, he sets out on a last-ditch mission to become her ideal type… even if it means becoming a swole “muscular man” overnight!