Age: Unknown (17-18 speculated only)

Height: 152 cm (5 ft)

Occupation: Student (grade 11-12), SOS Deputy Vice Commander

Mikuru Asahina, a shy and timid girl with a childish naïveté, is the only character other than Kyon to be brought into the SOS Brigade against her will. She is defined by Kyon to be extremely cute, and is often sexually harassed by Haruhi Suzumiya.

Considered one of the most beautiful girls in high school Mikuru is as kind, caring and thoughtful as she is beautiful. She easily gets scared or flustered, and is apparently prone to daydreaming as she can also be rather clumsy at times. Nevertheless, she can be surprisingly resilient and is capable of recovering from even the most discomforting of situations. However, because of her gentle nature she seems rather helpless most of the time. Kyon sees it as his duty to always watch over and protect her, although, when it comes to Haruhi there is no rescue.

Mikuru is the designated "mascot" of the SOS Brigade, serving as a way to attract interest and members by using her attractive physical qualities—her cute face, trim figure, and noticeably sizable bust. She was "voluntarily arrested" by Haruhi, who deemed it necessary to have an alluring lolita type in the club. Her sex appeal and innocence is often exploited by Haruhi to procure resources. Mikuru is on a regular occasion forced to wear any outfits that Haruhi buys for her. Haruhi also sees it fit that Mikuru is unable to dress and undress by herself most times and often does it for her, much to Mikuru's considerable—and vocal—distress. So far, Mikuru has worn the following outfits: maid, waitress, nurse, frog costume, cheerleader, miko, and the infamous bunny-girl.

The name "Mikuru (みくる)" is derived from "Miku" which when written in Kanji is "Mirai (未来)" ("future" in Japanese).