Mouse Anacreon is a mostly nonspeaking autistic fifteen-year-old attending mainstream high school classes. When he meets Friendly Ghost Anna Kinoshita, he learns that he's a sensitive who can perceive things that others can't, and that he is needed to save the world.
Mouse contains examples of:
- Calling Parents by Their Name: Mouse's mom has always said that, since it's just the two of them, he should call her June. Mouse didn't realize the other kids called their parents "Mom" and "Dad" until he was in kindergarten.
- Empty Bedroom Grieving: After Anna died, her family got rid of her medical stuff and put away a few of her figurines, but otherwise left her room the way she left it - dozens of anime figurines on every surface, posters for Japanese bands, dozens of light novels and anime DVDs, stuffed anime creatures on her bed, and a bedside lamp shaped like a Japanese lantern. Anna is embarrassed when Mouse sees it.
- Eyes Always Averted: Mouse can't make eye contact without being painfully overwhelmed by the flood of information. He mostly tells people apart by looking at their shoes, and only briefly glances at their faces to learn what they look like.
- Furniture Blockade: When Helene and Argo break into Mouse's building, he pushes his chair, boxes of books and DVDs, a trash can, and a mattress in front of the door to buy time until Anna arrives. It only lasts a few minutes, but that's enough for Anna.
- Hermetic Magic: June teaches Mouse to do magic that involves drawing out complicated sigils on pieces of paper and using his mind and energy to activate them.
- Hippie Name: Bliss has an older brother named Rain who's off at prep school.
- I See Dead People: Normally only babies and animals can see ghosts, and most adults who can see them only see a shadow, or static. Mouse has the rare ability to see ghosts in detail because he can perceive things without looking directly at them - when he does try to look at Anna, she disappears.
- Laser-Guided Amnesia: When some students witness something they shouldn't, Vallis shines a light from a small device at their foreheads, causing them to fall asleep. They wake up the next day with only a vague recollection, like a nightmare.
- Mama's Baby, Papa's Maybe: There are two candidates for Mouse's father: a sorcerer known as Priest, and an embassy worker who left before he even knew June was pregnant. June thinks it was probably the embassy worker.
- Minor Living Alone: Bliss tells Mouse that her parents spend most of their time in Hong Kong, leaving her alone in their suburban home. Actually, her family doesn't exist in this timeline. She "borrowed" a vacant house in the suburbs when she traveled back in time.
- Missing Mom: Anna's mom left after her death, leaving her surviving brother Kai alone with their dad Greg.
- Occidental Otaku: Anna actually does have Japanese ancestry, but in her efforts to reclaim her heritage she went way overboard, at least in the opinion of Kai, who thinks she should have just read a book about Japan or something.
- Only Known by Their Nickname: Mouse's real name is Simon, but no one uses it, and he corrects anyone who does.
- Parent with New Paramour: June starts dating Greg, leaving both of them with less time for their kids. Kai resents Mouse and June for "stealing" his dad.
- Pocket Dimension: Emotion eaters use a spell called the Antiochus Algorithm to unmake and remake the world, creating a pocket universe of Alien Geometries where, like in a video game, trying to leave one side of the map makes you reappear at the other, causing a constant rain of groundwater from the sky. The surviving humans live in starvation and terror, which is great for the monsters.
- Poltergeist: When Anna first died about a year and a half before Mouse meets her, she was desperately lonely and kept trying to get living people's attention, mostly by pushing things around, breaking things, and turning the TV off. But nobody realized a ghost was responsible. Finally she managed to pick up a pencil. Bliss walked in on her just as she was about to start writing and was horrified by the sight of a pencil apparently standing on its point. Anna realized that all her attempts at communication were only terrorizing the people, and she gave up until she met Mouse.
- Really Moves Around: Mouse and June move every year or two.
- Reincarnation: Helene is thousands of years old. Every time she dies, she's reborn in a new body. In each life, she gets a normal childhood before the Past-Life Memories come back during adolescence.
- Set Right What Once Went Wrong: Bliss was born in the pocket universe and has gone back in time to prevent its creation. She's actually gone back many times, each time resulting in a Stable Time Loop and her death, but she hopes that this time she'll be able to break the cycle.
- Shapeshifting Excludes Clothing: Helene turns into a tanuki to search Mouse's room. When she transforms back, he finds a naked girl in his bed.
- Shock and Awe: When the school is attacked by three azazim (essentially sentient zombies), Mouse kills two of them by summoning lightning from the sky.
- Signature Scent: Anna smells like lilacs.
- Synchronization: Priest helps Mouse use his powers to give Anna a physical body that's magically linked to his. Now they can feel each other's pain and emotions and catch snippets of each other's thoughts, and Anna complains about the taste when Mouse drinks tea.
- Time Stands Still: During his fight with the azazim, Mouse stops time for about ten seconds, enough time for him and Bliss to run to a better position.
