Seiji Matoba

Born on November 1st. Blood type AB. Height 174 cm. His hobby is collecting spirits for "shiki" (?). He is the current head of the largest exorcist group in the series, the Matoba Clan. He refers to himself as "watashi." A man with long black hair, he often carries a paper umbrella and wears an eyepatch with a pattern over his right eye. The eyepatch is to protect his right eye, which is targeted by a spirit due to a broken promise made by an ancestor of the Matoba family, who promised to let the spirit eat his right eye in exchange for help with a job. The area covered by the eyepatch is said to have a severe scar, but details are unknown. However, he did not wear an eyepatch or have any visible scars during his high school years. He is one year younger than Shuichi. His high school uniform was a gakuran.

The Matoba Clan is a group that unites exorcist families and was established as a mutual aid organization to protect member families that did not produce ability users from spirit retaliation due to the aforementioned circumstances. They share information and cooperate to confront powerful spirits. Exorcists are generally individual entrepreneurs, but the Matoba Clan operates like a company, allowing them to handle more jobs. Because of this, they are not well-regarded by their peers.

Initially, he recognized Takashi as "Shuichi's companion," but after Takashi, who was captured by the Matoba Clan, subdued a shiki with his bare hands and escaped with the help of Nyanko-sensei in his Madara form, he became interested in him. He eventually learns that Takashi is the grandson of the famous exorcist Reiko Natsume. When he captured Takashi, he found the Book of Friends among his belongings but dismissed it as mere scribbles. After that incident, he wrote a letter to Takashi (see Shuichi's section) and further invited Takashi to join the Matoba Clan. Takashi is aware that Seiji knows about the Fujiwara family and is threatened with revealing what Takashi sees and encounters to Shigeru and Touko. Since being deceived by Nanase, the Matoba Clan and Takashi have had a series of unfortunate encounters, and Takashi has been caught in the crossfire of the Matoba Clan's troubles more than once. Therefore, he views them as dangerous and believes that the existence of the Book of Friends must never be known.

He appears in the anime from the third season. In the latter half of the second season, his name is mentioned by Nanase and Natori, but he does not show his face.