Shiina Usami (宇う佐さ美み 椎しい奈な, Usami Shīna?), is a character in The 100 Girlfriends Who Really, Really, Really, Really, Really Love You. She is Rentarou's 28th girlfriend, and a third-year student at Ohananomitsu High School, in class 2-6. She was a suspicious girl that appeared out of nowhere and blended into Rentarou Family before officially joining them later. Shiina prefers to be addressed by the nickname "Usa-chan" (うさちゃん, Usa-chan). Shiina is first introduced as an unknown character who slips into the Rentarou Family as they are sharing their favorite photos of Rentarou—though he busts her cover as soon as he meets his girlfriends on the roof, due to not recognizing her. Shiina has severe autophobia, feeling lonely very easily, and is unable to do things on her own (such as going to the bathroom). She also fears empty spaces and singular objects, preferring to see objects crammed together or densely packed instead. Shiina admits that despite her desire to be with other people, she would end up being a nuisance and pushing them away. She then saw the Rentarou Family, and in the desire to be part of their group, she stalked them, memorizing every single detail about the group so she could fit in with them.