Based on available information, Yoshiko Koizumi, nicknamed Yocchan or Yotchan, appears in some adaptations of the Obake no Q-Taro franchise as a female classmate of Shōta Ōhara. Specific details regarding Yocchan's background story, character development, or her role in the film "Obake no Q-Taro: Susume! 1/100 Daisakusen" are not provided within the given sources. The documented character descriptions for the franchise primarily focus on Q-Taro, members of the Ohara family, and other ghost characters like U-ko and Doronpa.