Shinobu Maehara is a 14-year old schoolgirl who, after a bad start in which Keitaro lied about being in Tokyo University and his subsequent failed attempts to make it up to her, develops quite a crush on Keitaro (or Senpai - a Japanese term for senior - as she calls him). Shinobu is also a boarder at the Hinata House, in Room 201.
In the anime, she is first introduced as a grieving girl who has run away from home due to domestic turmoil, however, in the manga she is already at the Hinata House when Keitaro arrives.
She is quite skilled in both cooking and housechores -- her family once owned a restaurant in town prior to their divorce (the divorce does not actually occur in the manga, merely a feud).
She is overly caring of other's feelings, although this subsequently contributes to her own emotional frailty. Towards the end of both the manga and the anime, it becomes unclear whether she wishes for Keitaro to be with Naru or herself. By the time Keitaro and Naru get married, Shinobu is depicted as having gained great confidence in herself.
Shinobu's best friend is Kaolla, who seems to consider her more than just friends.
One reason Shinobu has a crush on Keitaro is they actually have somewhat similar personalities, particularly in the manga where she bears the brunt of much embarrassing humor.
Shinobu moves into the Hinata Apartments after her parents divorce. Part of the reason is her great fear of uncomfortable or embarrassing situations, which emerges from time to time during her stay in the Hinata Apartments.
She's generally very shy and quiet, but her time in Hinata will eventually warm her up to new friendships.She's the friendliest of the residents, with no angst against anyone and with no one disliking her. That's why she's my favorite character. She's somehow similar with Naruto's Hyuuga Hinata. (Hmm, and the name of the dorm is Hinata...) She's very practical and very diligent since she had to take care of herself a lot before she moved in. She's a good cook who frequently does the meals for the residents. And she's perhaps the only resident who treats Keitaro with any consistent respect. She's always kind to him when no one else is. Shinobu has a crush on Keitaro, but she keeps it respectably low-key, showing her appreciation in the simple things she does around the apartments.