The 22-year-old MC starts his senior year of college as an intern, and because his mother's best friend is going to work abroad, he is asked to help take care of the 11-year-old brother who is attending school in the same city. From then on, a mature and vicious primary schooler and a gentle and stingy older brother live together, because they played together when they are young, the two got close quickly, starting a hilarious and heartwarming life of living together. Although the two have no blood relations, they are closer than relatives.