Sawada Utako (彌砂)

In a world where humans and demons are in an endless war... One day, the demon king, Gil, arrives in the Kingdom of Hazelbard, a large human territory. Gil proposes a "truce" to the humans on the condition that neither side will invade the other's territory. However, due to a scheme by the queen, who is also his stepmother, to credit the agreement to her son Clemon, Princess Estelle is forced to marry the demon king in exchange... (Source: Cmoa, translated)

Rio Ichikawa has always been a serious person and has never been good at getting involved with other people since she was a child. One day, Rio is secretly excited when she is assigned to work on the same team with Nanase, a man who looks exactly like her ideal boyfriend who appeared in her dream. However, she is disheartened when Kato, another team member, and a client call her "serious" about her personality, which she is concerned about. Rio returns home depressed, and accidentally hugs a soaking wet man in front of her apartment building...?