“Oppa, I like it.” “Oppa, I love you.” An immature seventeen-year-old Goo Yeol-ae who fell in love with her friend's brother, Choi Kang-guk, and passionately courted her. He devoted 10 years of his life to being honest and sassy. Now, twenty-seven, I'm more hungry for love than to give.! Still, the strongest country is the strongest tsundere man. At a time when change was needed, they squirmed on the front of their love. Goo Yeol-ae, who got drunk and attacked Kang-guk's room, was found in Kang-guk's bed the next morning! 'If it's not the mind, I'll take the body.' Declared by a woman whose conscience worked. “Oppa, I’ll let you go. Instead, just stay with me for one night.” “Only once.” And, the promised night.. she has arrived Will the devotees be able to set a strong country? Maybe it's the huge design of the devotees who want to realize the rule of law, such as the effect of one night? Can I catch the strongest country, the '10-year unrequited girl' I want to be a devotee rather than courtship, and the 'strongest tsundere man'?