피트니스 센터의 개인 트레이너로 성공적인 커리어를 쌓았지만 가족에 대한 무거운 의무를 짊어진 효심. 4남매 중 유일한 여자이지만 자기중심적이거나 허황된 꿈만 좇는 세 오빠의 뒤치다꺼리를 하는 데 바쁘고, 유일한 안식처가 될 어머니는 오빠들 편만 들어 효심을 속상하게 한다. 게다가 까칠하고 꼼꼼한 신입 회원 강태호는 효심을 지친 마음을 제대로 자극한다. 이제 효심은 그 누구보다 자신을 소중하게 여기는, 독립적인 삶을 살기로 결심한다.
Hyo Sim has carved out a successful career as a personal trainer at TS Fitness, but her family obligations start to weigh down on her. Being the only girl among her four siblings, she is always the one handling the less desirable tasks and financial woes for her eldest brother, who focuses solely on his own family, her intelligent yet egocentric second eldest brother, and her youngest brother, who chases dreams of financial windfalls. Her only refuge in this constant battle against her demanding siblings is her mother, who unfortunately only sides with her brothers. Faced with adversity on all fronts, Kang Tae Ho, a meticulous new gym member, becomes the catalyst that pushes her over the edge. She decides that nothing else matters except regaining control of her life, and she takes the first step toward finding peace in her life.