Once Upon a Boyhood

Onyang's bully Byung-tae transfers to Buyeo, and he feels daunted by the thought of adjusting to his new school. However, the bullies he encounters at his new school only watch Byung-tae's every move.

Byung-tae tries to tell her that he is being mistaken for the legendary fighter 'Asan Baekho', but misses his chance. Then, he saves Seon-hwa, the queen bee of Buyeo, from an awkward situation.

Jong-min, who had Seon-hwa stolen by Byeong-tae, storms into Nonggo to have a showdown with Byeong-tae. Byeong-tae and his group, enraged by this, prepare for a large-scale war with Buyeo Technical High School.

Kyung-tae transfers to the same class. Byeong-tae has an intuition that he is Asan Baekho. Meanwhile, someone comes to find Byeong-tae, who is on a sweet date with Seon-hwa.

Ji-young advises Byung-tae, who is running for student body president, not to run, but Byung-tae ignores her. Meanwhile, someone appears who irritates Byung-tae.

The real Asan Baekho is revealed, and Buyeo Agricultural High School begins to be turbulent. Byung-tae returns to his life as a lowlife. Byung-tae's love and friendship become increasingly endangered.

Byung-tae loses everything, but Kyung-tae runs for student council president, throws a grand birthday party, and even wins Seon-hwa. Meanwhile, the long-awaited student council president election day approaches.

Byung-tae's father, who was framed, is taken to the police station, but Byung-tae can do nothing. In the end, Byung-tae decides to gain strength for revenge, and Ji-young helps him.

The breathtaking revenge of Byung-tae, hidden behind a mask, begins. Byung-tae receives special tutoring from Ji-young and begins a one-on-one customized operation to defeat the agricultural high school gang.

Ji-young is worried as she watches Byung-tae's injuries worsen. Meanwhile, Byung-tae comes up with a trick to defeat Asan Baekho. Will Byung-tae's revenge be successful?