In your website, you state, “Part of the scroll depicts a tale of a legendary Japanese empress. First recorded in the eighth century, the tale recounts events claimed to have taken place more than four centuries earlier. Today, the story is viewed by historians around the world as fictional. There is no evidence that a Japanese invasion took place at this time.”
The above comment is not correct. There are many Japanese and Chinese historians who maintain that there is evidence that a Japanese invasion took place at this time. It is true that the Japanese empress most likely is a legendary figure and her existence is considered fictional by historians around the world, but the invasion itself was not regarded as fictional by historians.
These are some example evidence.
(1) The stele of King Gwanggaeto of Goguryeo
This stele was erected in 414 by King Jangsu as a memorial to his deceased father. It is one of the major primary sources extant for the history of Goguryeo in Manchuria.
You can read both the original and English translated text inscribed on this stele in this website (http://www004.upp.so-net.ne.jp/teikoku-denmo/english/history/kohtaioh-hi_hibun.html). As you can read on this stele, it says, “Since Baekjan [an ancient country in the Korean peninsula] and Silla [another ancient country on the Korean peninsula] are originally subservient states (of Goguryeo), they paid tributes to Goguryeo. And since the Sinmyo year (CE 391), the Wa (Japan) came across the sea, and defeated Baekjan, [(then xxx-ed Sil]la and made them subjects.”
Although some Korean historians insist that this stele was altered by a Japanese person (there is no evidence that this was done), both Chinese and Japanese historians consider this description as evidence that a Japanese invasion certainly took place in the 4th century.
The Book of Song is an historical text of the Liu Song Dynasty of the Southern Dynasties of China. It covers history from 420 to 479, and is one of the Twenty-Four Histories, a traditional collection of historical records. It was authored by Shen Yue from the Liang Dynasty (502-557) and contained 100 volumes at the time that it was written.
One of the volumes contains information about Wa (Japan), and you can read the original text of this in this website (http://www2.plala.or.jp/cygnus/R7.html). This does not have English translation, but I believe one of the staff members in your museum must be able to read old Chinese texts. According to this Chinese historical record, the letter to the Chinese emperor at that time sent by a Japanese emperor, Emperor Yuryaku, states that the Japanese control covered the southern part of Korean Peninsula.
(3) Book of Qi Dynasty
The Book of Qi or Book of Southern Qi is a history of the Chinese dynasty, Southern Qi covering the period from 479 to 502, and is one of the Twenty-Four Histories of Chinese history. It was written by Xiao Zixian during the succeeding Liang Dynasty.
One of the volumes relates evidence about the Japanese emperor, Emperor Yuryaku. The title of this Japanese emperor in this Chinese history record is the Subjugating General of six areas in Southern Korea. You can read the original Chine text in this website (http://www.ceres.dti.ne.jp/~alex-x/kanseki/nsei-tonan.html).
In addition to the above mentioned evidence, some other information is discussed out by Chinese and Japanese historians who maintain that the southern part of Korea was subjugated by Japan during some time in the 4th and 5th centuries.
It is my understanding that you are showing “Stories of the Shinto deity Hachiman and shrines dedicated to him” as an art object, not a historical material. It seems to me that the attitudes of those Korean people who are asking you to remove this artwork because the historical view depicted in this scroll does not correspond to their inaccurate history are unaware of the true historical record.
I hope you will not be unduly influenced by their unreasonable and historically inaccurate requests.