A unique love story that tells the unfortunate tale of Sang Doo and his long lost childhood love.

International singer/actor Jung Ji Hoon (Runaway: Plan B), better-known as Rain, stars in Sang Doo, Let's Go to School!, one of his first dramas. Joining him is Gong Hyo Jin (Pasta) who is renowned as one of the queens of romantic comedies. These two stars' chemistry sparks in this unique love story that tells the unfortunate tale of Cha Sang Doo and his long-lost childhood love, Chae Eun Hwan. Dealing with such problems as wrongful imprisonment, single fatherhood, and enrolling in high school as an adult, Sang Doo is a man with many problems just trying to make ends meet. Sang Doo and Eun Hwan spent their childhood as best friends, but after an unfortunate accident, Sang Doo was separated from his love. Years later, Sang Doo becomes a gigolo to pay his sick daughter's medical bills. By chance, he finds Eun Hwan, who is now working as a high-school math teacher. In an attempt to regain her love, Sang Doo re-enrolls, hoping to win her over.