Seo Dogyeom, the young master of a mansion, and Yoon Seowon, the housekeeper's son, share a secret bond despite their different social statuses. After a kiss, Seowon falls in love, but Dogyeom abruptly leaves to study abroad. Five years later, Seowon, now an adult, is about to leave the mansion when Dogyeom returns and offers him a role as his pheromone partner.