A master of triggering romantic flags. He is extremely shy regarding romance and has been in love with his middle school childhood friend, Haruna Sairenji. He is naturally athletic, but his academic performance is somewhat lacking. He suffers from extreme misfortune with women and is a chronic victim of 'lucky lecher' accidents.

The First Princess of Planet Deviluke, characterized by her long pink hair. She fled her home planet and came to Earth. She fell in love at first sight with Rito Yuki, whom she happened to meet upon arrival, and is now living with him while striving to become his ideal bride. As an alien, her words and actions often defy Earth's common sense, frequently shocking those around her.

She has a gentle and refined personality and performs well academically. A member of the tennis club, she has a fearful side, hating horror stories and crying easily when scared. When her fear reaches its limit, she enters a berserk state that no one can control. She has been Rito's classmate since middle school. She likes Rito but is too shy and clumsy in love to confess her feelings (a trait shared by Rito).

Extremely serious and strong-willed. As a member of the Discipline Committee, she has a habit of trying to regulate public morals even in her private life. She detests anything unconventional or lewd, but she is actually very kind at heart.

Possesses transformation abilities that allow her to change parts of her body into any shape at will. She has been alone since birth and lived as an assassin, struggling to find value in her existence. Her real name is never revealed, and she is called Yami-chan or Yami by those around her.

Rito's friend who has a very flighty personality. In contrast to Rito, he has a strong interest in the opposite sex and often drags Rito into trouble due to his ulterior motives, though he almost always fails.

The principal of Sainan High School, who can only be described as a pervert. He allowed Lala and the others to transfer to the school without any entrance exams simply because they were 'cute.' Ever since he peeked at female students bathing during a school trip, he has begun acting on his lewd impulses.

Rito's younger sister. She is very mature for her age and is a reliable person who handles the housework in place of their frequently absent parents. While she is a sensible person, she harbors feelings for her brother that go beyond sibling love.

Lala's younger sister and the Second Princess. She has a complex about her flat chest and possesses innocent, age-appropriate views on romance.

The younger sister of Lala and Nana and the Third Princess. She has a sadistic streak and is skilled with machinery, though her inventions are often defective and frequently trigger trouble.