“Twenty-Five, Twenty-One,” tells a love story between Na Hee-Do (Kim Tae-Ri) and Baek Yi-Jin (Nam Joo-Hyuk).
Na Hee-Do is a member of her high school fencing team. Due to the South Korean financial crisis, the high school fencing team gets disbanded. Getting through all the difficulties, she becomes a member of the saber fencing national team.
The South Korean financial crisis also causes Baek Yi-Jin’s father’s business to go bankrupt. This leads to a life change for Baek Yi-Jin, from living the life of a wealthy person to a poor person. While studying, he works part-time jobs like delivering newspapers. Later, he becomes a sports reporter for a broadcasting network.