He's a novelist but, as his short stories don't allow him to live properly, he often works for the press. He was in the same college as Kyougokudou and hangs around with him. He's often teased by his friends in regards to his poor social skills.  During the war, Sekiguchi fought with Kiba in the same regiment. While the details about this period are unknown, it is implied that Sekiguchi is a deserter who suffers from psychological disorders because of what he saw and did during the war.  He has a wife named Yukie.

Between August and October, 1952, a series of unusual crimes takes place in Musashino and Mitaka: the attempted murder of 14-year-old Kanako Yuzuki, Kanako's abduction from the strange research "hospital" where she was recovering, then abductions of other girls, followed by their severed limbs in custom-fitted boxes being placed in surrounding towns. News editor Morihiko Toriguchi and crime fiction writer Tatsumi Sekiguchi investigate with the help of onmyōji Akihiko Chūzenji. Meanwhile, Tōkyō police detective Shutaro Kiba searches for Kanako, despite Kanagawa police having jurisdiction; and the lawyer for the estate of Kanako's grandfather hires private investigator Reijiro Enokizu to find Kanako, as well. Their investigation uncovers bizarre truths and dark family secrets along the way.
 
(Source: Anime News Network)

[Profile](https://osawa-inc.co.jp/men/kiuchihidenobu/)

Manga adaptation of the first novel in Kyougoku Natsuhiko's award-winning Kyougokudou Series.
 
Tokyo, 1952: The bizarre case of a missing doctor and his supernaturally pregnant wife captures the imagination of novelist Sekiguchi Tatsumi, so he enlists the help of an old friend, Chuuzenji Akihiko, a bookstore owner and part-time exorcist who begrudgingly agrees to help investigate the disappearance. They'll face a family's darkest secrets... Secrets that Sekiguchi himself can't escape.

Manga adaptation of the second novel in Kyougoku Natsuhiko's award-winning Kyougokudou Series.
 
Right after the war, Showa era in Japan. Kusumoto Yoriko and Yuzuki Kanako who attend an all girls school plan to take the last train to go to the lake. However, Kanako ends up getting run over by the train. Tokyo Metropolitan Police Department's Detective Kiba who happened to be there when it happened, is asked to watch the confused Yoriko. Kiba goes with the worried Yoriko to the hospital Kanako is taken to, and there Kiba meets a woman who calls herself Kanako's sister; Yuzuki Youko. That happened to be the actress Kiba had been admiring, Minami Kinuko.

Manga adaptation of the third novel of Natsuhiko Kyogoku's Kyougokudou Series.
 
"If there's such a thing as a soul, does it remain in this world as long as the bones exist? Will all of my sins and sorrows remain in this world forever?"
 
Tokyo, 1952. A beautiful, mysterious woman who's haunted by dark dreams claims to have murdered her ex-husband... three times. Meanwhile, a small seaside town is terrorized by a bizarre series of deaths. Four seemingly separate murders are linked by strange, unsettling dreams of bones... Is something supernatural going on, or are the real demons found in the depths of the human mind? This complex case reunites the sleuths from Ubume no Natsu and Mouryou no Hako: onmyoudou practitioner Chuuzenji, horror novelist Sekiguchi, police inspector Kiba, psychic detective Enokizu and journalist Atsuko.

Our setting is in Tokyo in 1948, just right after the war. Kanna Kusakabe had just become a second-year at a high school when she meets the new language teacher, Akihiko Chuuzenji. 

Mysterious supernatural things keep happening around Kanna. Once again today, Kanna is going to open the doors to the library prep room to seek help from the surly Chuuzenji-sensei who is waiting inside. 

A high school supernatural mystery featuring the unlikely duo between a teacher and a high school girl is about to begin! 

(Source: Pony Canyon, edited)

Manga adaptation of the fourth novel of Kyogoku Natsuhiko's Hyakki Yakou series.
 
The story follows antique store worker Imagawa, aging doctor Kuonji, and writer Sekiguchi, who are all fascinated by mysterious events happening in Hakone, including a series of murders of Buddhist monks and a little girl in a kimono who wanders through the mountains.

A side story that reveals the investigative notes that Atsuko, the younger sister of the main character Akihiko Chuzenji, wrote about the brutal dismembering incidents in the main story.
 
(Source: Anime News Network)

In 1950s Tokyo, only the Rose Cross Detective Agency can tackle the cases that the police won't touch. Enokizu is an eccentric private eye with psychic abilities, and Chuuzenji is a surly used book store owner with an encyclopedic​ knowledge of obscure trivia. Together with their associates, they seek justice for the victims.


Manga adaptation of the fifth novel of Natsuhiko Kyogoku's Hyakki Yakou Series. The story begins with a supernatural murder mystery in an all-girls school. Sayako and Miyuki both attend a high class private religious all-girls school, and one of the bonds of their friendship is that neither of them come from a prestigious family. One day, Sayako confides to Miyuki that the teacher Honda-sensei is sexually abusing her. When Sayako hears a school legend that involves asking a demon to curse someone to die, she and Miyuki investigate the possibility. 
Miyuki, an atheist, doesn't really believe in the idea of curses, even though she has a schoolmate, Yuko, who has supposedly used this method to have someone killed. Nevertheless, she supports Sayako in carrying out the ritual, in the hopes that it will give her some peace. However, after they speak with Yuko, they must face the fact that the curse may be dangerously real, and may carry with it horrific consequences. Miyuki's world is quickly spiraling into a nightmare!

Kusakabe Kanna, who has advanced to the second year of a new high school, meets Akihiko Chuzenji, a new instructor of Japanese. Chuzenji always read books with a bad mood. A combination of teachers and students confronts a series of strange cases.