To help Hoshina and her husband get more exercise, they started running together with Kayama, a client of Hoshina's. Seeing Ai's innocent appearance and her rapid improvement in her time, Kayama, a widower, feels lust for the first time in a long time... Her body, which has hardly been loved by her husband, tries to resist but is engulfed in waves of pleasure. Their relationship has crossed the line and continues to run wild. Every time they meet, they sweat with pleasure, but...