Мінамі Санае

A friend of Wakaba, Sanae is a weak and shy girl who joins the trip to Kanenone because her doctors believe that the fresh country air will be beneficial to her health. Her need to take medication on a regular basis is highlighted in several episodes. Sanae has a much younger appearance than the rest of the major female characters. This draws the attention of Tenjin, who has a fetish for "little sister" types. Unfortunately for Tenjin, his unusual and over-enthusiastic advances only manage to frighten Sanae away from him. Source: Wikipedia