During a corporate training program at his workplace, younger brother Hiroki comes to stay at his older brother's house for a while. One day, Hikari, wearing tight, sexy leggings while working out, asks Hiroki to help her stretch. As she bends over, the tight fabric of her leggings splits open at the rear due to the pressure of her plump, shapely buttocks, unintentionally exposing her naked backside. Unable to resist the pent-up desire built up during his training, Hiroki's rock-hard cock surges forward and he uncontrollably thrusts it deep inside her.