The narrative of Marriage Royale centers on Tsukasa Hinomoto, a high school student who is informed by his parents that he was adopted. They further reveal that his biological father is a manager at a major corporation, implying he possesses significant wealth and influence. Because his real father desires a suitable wife for his son, he organizes an event called Marriage Royale. In this competition, attractive women from across Japan gather at a school constructed specifically for the purpose to compete for the position of Tsukasa's fiancée. The facility is situated on a secluded island off the coast of Japan, where Tsukasa is transported to reside in a mansion under the supervision of two twin maids: the older sister, Miku, and the younger sister, Miu.