in/spectre

In this universe, yokai are more than just monsters; they exist based on human belief and folklore. The series frequently features traditional creatures (like Kappa or serpents) as well as modern urban legends (like the "Steel Lady Nanase"). The spirits rely on Kotoko to help them solve problems, mediate disputes with humans, or deal with rogue specters that threaten the balance of the spirit world.

The older cousin of Kuro, whom he visits in the hospital on a regular basis. She is diagnosed with a long-term illness, but is in reality unhealthy only because she has received the same powers as Kuro, just with more negative side effects. She utilizes her abilities to create Steel Lady Nanase, intent on bringing chaos to the world.

A young police officer and Kuro's former girlfriend. She was originally set to marry Kuro after graduating from college, but becomes fearful after witnessing Kuro's regenerative powers and leaves him. She meets Kotoko while they both look for clues on the vengeful spirit of Karin Nanase. This leads them to team up along with Kuro to take the spirit down.

A young university student with total healing and limited future manipulation abilities, which he acquired at a young age due to his grandmother pursuing experiments performed by their ancestors by having him unknowingly consume yōkai flesh. At the cost of his life, he may select a branch of the near future with a somewhat high probability of occurring and make it a reality. His healing powers revive him each time, which grants him a consistent method to control the future. Due to his status as both human and yōkai, he is often seen as a major threat to even the strongest yōkai. Additionally, his flesh is poisonous to yōkai that attempt to eat him. He is currently in a relationship with Kotoko, though he makes it clear that he is constantly annoyed by her.

A young university student with one eye and one leg. She loses her an eye and leg at a young age after she accepts the yōkai's request for her to become their Goddess of Wisdom; because of it, she receives a fake eye and a prosthetic leg, and walks around with the assistance of a cane. Her role as the Goddess of Wisdom is to mediate disputes between yōkai and provide them with knowledge and wisdom when necessary. Kotoko possesses genius-level intellect and is capable of high-quality deductive reasoning, making her an excellent detective. After falling in love with Kuro, she must wait a few years before he splits with Saki, and approaches him to become his new girlfriend. They eventually get together, though she often annoys him.

While struggling to get past a break-up with his girlfriend, Kuro Sakuragawa was approached by Kotoko Iwanaga, a girl who declared that she has been in love with Kuro since she met him two years ago. She then tells him that she is a sort of Goddess of Wisdom where she serves as the intermediary between the real world and the supernatural world. Kuro, of course, doubts her at first but after fighting a yōkai in a library, they reveal to each other their true identities. Kuro is actually part monster due to having eaten two different yōkai flesh, giving him the abilities to heal from any wound and to have limited control over the near-future. Kuro agrees to help Kotoko on her various adventures as the peace-keeping Goddess of Wisdom, soon becoming a couple.