The reputation of a prize-winning writer of a number of well-regarded books on Protestant theology is under a cloud after an investigation found that quoted material in one of his works does not appear to exist.

Tomoaki Fukai is head of Toyo Eiwa Jogakuin, an educational institution headquartered in Tokyo's Minato Ward that operates a range of schools for girls and women from kindergarten through university and graduate school.

Alerted to apparent irregularities in research activities related to a book published in 2012 by Iwanami Shoten Publishers that looked into the relationship between German nationalism during the Weimar Republic and Protestantism, the institution set up an internal investigative committee.

Over the course of four pages, Fukai focused on a religious scholar by the name of Carl Loevler who purportedly writes about the significance of the German philosopher Friedrich Nietzsche to religious studies today.

But there are no bibliographic notes for the quoted material that show when and where it was originally published.

Atsushi Koyanagi, an associate professor at Hokkai-Gakuen University and expert on the history of German Christian philosophy, sent an open letter to Fukai in March through the channels of the Japan Society of Christian Studies.

What was described as a "tentative" response reached the society headquarters on July 2, which was published in the society's journal dated Sept. 25 along with Koyanagi's initial letter.

In his letter, Koyanagi explained that he examined other works, both published and available over the Internet over the past 30 years, to find anything associated with the "Carl Loevler" that Fukai included in the index of his book.

Koyanagi said he could not find a single instance of the reference that Fukai cited, nor even uncover a scholar with that name.

Koyanagi said, "This is not simply a 'mistake.' I also found that some of the contents appear to have been simply Fukai's creation."

In its Oct. 25 edition, the weekly Shukan Shincho described this exchange in detail.

However, Fukai claimed that the misunderstanding may have arisen due to the manner in which the German name is translated into Japanese. He contended that the actual spelling in German of the scholar he referred to was "Carl Fritz Loffler."

In his response to Koyanagi, Fukai gave the name of a German catalog and said while that document was not widely known in Japan, it contained the scholarly work that he used in his book.

However, Koyanagi also examined that catalog but could not find the quoted material.

A reporter for The Asahi Shimbun read the same catalog and reached the same conclusion.

When a subsequent inquiry was made of Fukai, he sent an e-mail apologizing for having named the wrong catalog as the source of the quoted material.

Toyo Eiwa University does its utmost to protect the integrity of the institution, particularly if questions are raised about published research by one of its professors. For this reason, it set up an investigative committee that includes outsiders to scrutinize his research.

Sadamichi Ashina, editor of the journal of the Japan Society of Christian Studies, wrote in the publication, "The society must deal with this issue in a sincere manner as it relates to research ethics."

The Asahi Shimbun requested an interview with Fukai, but he sent an e-mail that said he would have to wait until the university had completed its investigation.

Born in 1964, Fukai specializes in the history of German religious philosophy. He obtained his Ph.D.s from Germany's University of Augsburg and Kyoto University.

His book on Protestantism won this year's Yomiuri Yoshino Sakuzo Prize. A past work also won the Nakamura Hajime Prize.

(This article was written by Kentaro Isomura and Satoshi Ouchi.)