Riina Shima, also known as Riina
Riina is a young girl with tanned skin and a short, light brown, messy bob-cut. She has brown eyes. She wears a matching choker and sleeves which are black with small jewels hanging off them, along with a small necklace; a black strap vest which has been folded at the bottom under a white tank top; 3/4 length light blue denim jeans and black wedge sandals.
- A young woman living in the Invisible City. She is very quiet, and often her speech is short and separated by many pauses. She holds the belief that if she does not have to do something, then she will not do it, and so comes across as a rather lazy type of character. However, her physical ability is outstanding and she is in very good shape.
- Because resources in the Invisible City are limited, she works together with Seiji as a purveyor, and travels to the outside world to collect goods that can't be received within the city. Since Souhei has been living in the city, they usually go together. Souhei has compared her style of getting about like parkour.
- Though it is not revealed at first, when Souhei meets his dad towards the end of the book, he tells Souhei that Riina's last name is 'Shima' and that they are related.
- She has a tendency to pat herself on the head sometimes.
- In the same Riina (里稲), Ri (里) roughly translates to 'home town', 'village' or 'country home'. Ina (稲) means 'rice plant'. Shima (嶋) means 'island'.