During a vacation to the beach, Squad 13 accidentally discovers remnants of an abandoned modern city and go exploring. Kokoro comes across a medical office and finds the baby book on the floor. Although she is aware the book contains information, such as pregnancy and childbirth, that is considered forbidden knowledge and even having it is a serious violation of APE’s regulations, Kokoro secretly brings it back to Cerasus and began reading it. She quickly learns the origins of humans and the concept of intimacy and procreation.
For several months, Kokoro keeps the book hidden from her squadmates, except Mitsuru, who agrees to keep it a secret. However, the book makes her question the ideals of APE, especially Papa’s claim he was solely responsible for creating all the children and that their one purpose in life is to pilot the FRANXX. This causes her to be more open about her doubts of the adults and changes her perspective of how they all live their lives. In addition, Kokoro is able to connect the link of intimacy to emotions, which makes her more assertive in her feelings for Mitsuru.
Due to becoming fascinated with the contents of the book, Kokoro develops an intense yearning to become a mother but she explains she wants to leave a mark for the future before she dies. Mitsuru eventually comes to share her perspective and they attempt to conceive a child. However, the book is discovered by the 9's, who report to Papa about the violation and, as punishment, Kokoro and Mitsuru’s memories of each other are altered. Because Squad 13 is deeply moved by Kokoro’s words about thinking about the future due to that she believes procreation represents hope for them, they rebel against Papa.
Due to learning about sexual intercourse from the book, Kokoro becomes pregnant with Mitsuru’s child and she gives birth to a girl.
- Fetal Development
- Infant Care