Mio Sawada is a high school student at Sainan High School and a close friend of Haruna Sairenji and Momioka Risa. She is a classmate of Rito Yuuki and Lala Satalin Deviluke. Mio was born on September 17, has blood type AB, stands 152.5 centimeters tall, and weighs 45.5 kilograms. She has brown hair often worn in two pigtails and light brown eyes.

Mio has a mischievous and cheerful personality. She is almost always seen alongside Risa, and she enthusiastically participates in Risa’s antics, which frequently involve teasing or groping other female characters, particularly Haruna and Lala. Despite this playful behavior, she is generally supportive and friendly toward her friends. She works part-time at a maid café called Sister CAFE, a job she took up because of her interest in cosplay. Mio is also a member of the school’s tennis club alongside Haruna and Risa.

In the story, Mio serves as a minor supporting character and provides comic relief. She rarely drives the plot but consistently appears in the background of school and social scenes, often as part of a duo with Risa. When Lala asks questions about Earth customs, Mio and Risa are quick to offer explanations, though these are often misleading or perverted. Her role remains consistent throughout the series, including in Motto To Love-Ru and To Love-Ru Darkness, with no significant personal development arc. She does not have any notable supernatural abilities or combat skills; her defining traits are her close friendship with Haruna and Risa, her love of cosplay, and her energetic, mischievous nature.