Jinnai's younger sister by about a year.

Nanami is highly independent and strongly entrepreneurial, going so far as to take payment from the high school's Broadcast Club to grill her brother over the fraudulent election results on campus television. When she's sent to El-Hazard, she's initially alone and is forced to take on a waitressing job to earn enough money to travel, but she eventually meets up with Makoto and Fujisawa at the Fountain of Arliman, where she is able to start a small business selling boxed lunches to the visiting priestesses. Nanami has feelings for Makoto, but she's never really had the opportunity to talk about a relationship with him.

Nanami's power gained upon entering El-Hazard is to see through the illusions of the Phantom Tribe, making her a viable defense against the greatest threat in the first OVA series.

Nanami in The Wanderers

The Phantom Tribe does not exist in the alternate timeline, and so instead Nanami has the same power to communicate with the Bugrom as her brother. Her past relationship with Makoto is also explored a bit more in detail, and she becomes good friends with Princess Rune Venus. As well, in the last episode of the TV series, Alielle describes Nanami and herself as "special friends", lending their relationship a certain homoerotic subtext, though this seems to be more along the lines of a big sister relationship.

(Source: Wikipedia)