Nagi Umino is the main male protagonist of A Couple of Cuckoos Series. He is a second-year student at Megurogawa Gakuen. He is the biological son of a hotel tycoon, but due to a mix-up after his birth is raised by a different family. Nagi seems to be obsessed with studying to the point that he studies day and night in order to achieve top marks. He is quite capable in pretty much everything, whether it is housework or schoolwork, proving his culinary skills multiple times by preparing delicious dishes everyday. He is a free-willed and determined person with a stubborn attitude to never give up. He is also naïve when it comes to the girls around him. Yet his kindhearted nature means that he will protect the ones that he cares about by doing everything in his power to help them.