She lost her parents at a young age and lives with her aunt. A 17-year-old girl who can see the Mimi-zu. She is beautiful, has a friendly personality, and can see the Ever-After beyond the doors. She travels with Souta to stop the Mimi-zu. She is Guest's childhood friend and best friend. When she closes her eyes while locking a door, she hears the voices of the people who once lived in those ruins. She has never been in a relationship. She speaks politely to Souta. She does not fear death and seems to have feelings for Souta.

A Closer and a university student. He is exceptionally handsome and travels to find and close Rear Doors. He closes the doors by sheer force, then inserts a key and recites an incantation to seal them. He meets Suzume and travels with her to close the doors. His incantation is: "I call upon the Great God of the Earth, the deity of our ancestors. For the mountains and rivers that have long been granted to us, with awe and reverence, I humbly... *He inserts the key* ...return them to you!" He is busy balancing his teacher certification exams with his duties as a Closer. He is like a close older brother to Guest and a partner in stopping the Mimi-zu. He has currently been turned into a three-legged toddler's chair (a keepsake from Suzume's mother). Like Suzume, he hears the voices of past residents when closing doors. He wears the key around his neck. He didn't realize Daijin was a Keystone until Daijin cursed him; now, based on Suzume's words, he seeks to reseal the cat. Even as a chair, he works hard to block the doors. He can move and speak, and he no longer feels hunger or thirst. When he locks a door, a mystical effect of yellow, orange, and blue light appears as a new keyhole is manifested. He comes from a wealthy family and dreams of becoming an elementary school teacher. By becoming a chair, the role of the Keystone was transferred to him, though he is unaware of it. He falls in love with Suzume during their journey.

Originally a Keystone driven into the earth to prevent the doors from opening, he was accidentally freed by Suzume and now takes the form of a cat. He refuses to become a Keystone again. He can speak and cast suggestions or curses on others. He wants to be Suzume's child. He has a mischievous, wild, and very childlike personality. He can transform into a giant cat when necessary. Male. He is very fond of Suzume because she liberated him. He instinctively knows where the next Rear Door will open. He leads Suzume's group to the next door while appearing to run away from them.

An evil deity-like entity that emerges from Rear Doors to cause earthquakes. The amount that leaks out depends on the door's size; the largest can cover an entire city. There are massive Rear Doors at the sites where the Keystones were placed; if these open, earthquakes could kill over a million people. It has no eyes, nose, or mouth, and does not speak. Its only goal is to exit the Ever-After and cause destruction. Once it fully emerges, it pauses to absorb the energy of the land, turning into a golden aura before crashing down. It takes the form of a giant worm.

A Keystone larger than Daijin. Currently in the form of a black cat, but transforms into a divine beast when closing doors. More mature than Daijin. Male. He can speak. Unlike Daijin, he wishes to return to being a Keystone to stop the Mimi-zu. He is currently free and can cast hypnosis similar to Daijin.

Suzume's best friend. Female, 17 years old. Simple-minded and blunt. She has noticed that Guest likes Suzume.

Suzume's best friend. Female, 17 years old. She knows a lot of internet rumors. She often bickers with Guest.

Souta's grandfather and a former Closer. He is currently hospitalized.

Souta's friend. An ordinary guy who smokes and can be a bit oblivious. He loves music.

Suzume's aunt. She is single and sometimes jokes that she can't meet men because of Suzume. She has a good relationship with Suzume and cares for her deeply. While she harbors a small amount of hidden resentment, her love for Suzume is genuine.