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. 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.
She is in fact a time traveller from the future with the purpose of observing Haruhi during the course of the story line. Mikuru often has trouble talking to Kyon because many of the things he asks about revolving around her powers are "classified". Mikuru's future self occassionally shows up as well, in order to properly guide the timeline to the correct path, and is notably more mature and knowledgeable than her past self. In order to differentiate between the older and younger versions, whenever the older self is present in the same time span, Kyon refers to her older self as Asahina-san (Big) and to the younger Asahina as Asahina-san (Small).
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 sizeable bust. She was "voluntarily arrested" by Haruhi, who deemed it necessary to have an alluring "Moe" 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.
