The fourth volume of Yagate Kimi ni Naru, containing chapters 17 to 23, was released by Dengeki Comics on June 27th, 2017 in Japan. The English translation licensed by Seven Seas Entertainment was released on February 20th, 2018.
Koyomi's script is about a girl (played by Touko), who is hospitalised due to an accident and suffers from amnesia. Having forgotten everything about who she is, she is visited by three people who were important to her: a classmate (Doujima), her brother (Maki), and her girlfriend (Sayaka). Each gives a different, conflicting perspective of who she was before the accident. She must choose which she believes to be her true self. In the first draft ending, she chooses to become the lover to her girlfriend. Yuu plays a minor role as a nurse.
To prepare for the play, the student council holds a training camp during the school break. The training camp turns out to be filled with tension, especially as the three girls have to share a bedroom and bath.
During the training camp, Touko displays remarkable acting talent due to her affinity for the role. It becomes increasingly evident that she is conflating herself and the character she is playing. Her identity issues are compounded by a realization that her perception of her sister, upon which she has based her identity, is starkly different to that of others who knew her. Noticing Touko's disquiet, Sayaka shares that she is aware of Touko's inner struggles and wants to help her. The two grow slightly closer.
After the training camp, Yuu invites Touko to her home. As her crisis of identity deepens, Touko tells Yuu that she hates herself, and thus must become someone else. She reminds Yuu not to fall in love with her. Yuu begins to realize that she loves Touko, but stops just short of admitting it, even to herself.
- The volume extras contained an omake of Yuu and Touko studying together, a map of the layout of Yuu's room, and a 4-koma of Maki and Doujima's time at the training camp.