Taneda is a middle-aged man, bald and with green eyes. He wears a pair of glasses and he is always seen wearing a kimono under a black haori (a traditional Japanese thigh-length kimono-style jacket, commonly worn by men).
Not much is known about his personality. According to Fukuzawa, Taneda has "a ridiculous personality, a strange man in terms of a normal person."
His ability Hail in the Begging Bowl (
Not much is known about his past. It's hinted that he helped on the creation of the Armed Detective Agency and was also the one who helped Osamu Dazai to find a job in the Agency after he left the Port Mafia.
Together with Ōgai Mori, Taneda is called for a meeting by Ango Sakaguchi at a ship near Yokohama Bay. As part of their deal in exchange for the mafia's services to handle the European guerilla organization Mimic, Taneda issues Mori a skilled business permit to recognize the illicit affairs of the mafia to be legal thereafer.
At the onset of the terrorism of the Decay of Angels, Taneda issues Ango with orders to kill the infamous murder association rather than arrest them. Though Ango is initially reluctant with his rash decision, Taneda explains to him that their duty as part of the Special Division sometimes requires bending the law and even sacrificing good people in the process in order to protect the peace of the country, especially from a terrorist group such as the Decay of Angels.
Later, while Ranpo Edogawa was searching for a lead on the Decay of Angels, he finds Taneda injured and bleeding out in a building. Taneda has been attacked by one of the three unknown members from the Decay of Angels, who has the ability to exchange the information they most wish to know for the information their enemy wishes to know the most. Consequently, the Decay of Angels members stole a page from the Book in exchange for information on what their goal is. In the aftermath, Taneda is hospitalized and is hinted to undergo operation, expected to regain consciousness within 40 hours depending on its success.
- It is very possible that he was Sōseki Natsume's pupil as well.
- Fukuzawa refers to him as "Taneda-sensei".