Shinobu-kun The Only Girl at an All Boys School, a gender bender game developed by circle 7cm. Released October 14, 2015. Available for download on DLsite.com for $4.00. Available for PC Windows. No voice acting.
Accidentally transformed into a girl, Shinobu must travel all across the school looking for the five magical books that will turn her back into a boy.
Source: N4G PC [NSFW] Gender Bender Hentai Game: Shinobu-kun – Hentai Reviews