For Yui, whose body had lost its firmness and who no longer had the confidence she once did, her daily masturbation had become a routine. Determined to reclaim her former glory, Yui decides to join a fitness gym. However, her true aim is to be near the handsome trainer. Under the trainer's guidance, the exercises become increasingly risqué, bordering on the erotic. Gradually, the activities escalate to include dildo squats, stretch blowjobs, and live insertion squats, marking the beginning of Yui and the handsome trainer's secret lessons...