#t/n: 'commentaries during a rainy night' is a scene from the first chapter:

[ikusayu-no-hana]

The time period is the Kanko era, one of the eras that took place during the 400 years of the Heian period. With Kasen Kanesada as the captain, Ookurikara, Ichimonji Norimune, Sanchoumou, Himetsuru Ichimonji, and Nansen Ichimonji travel to Heian-kyo.

This was because they had detected abnormalities surrounding the history of Murasaki Shikibu, author of the world's oldest full-length novel, The Tale of Genji.

While the Touken Danshi are scouring Heian-kyo in search of Murasaki Shikibu, they come across a woman being hunted down by a suspicious group. Kasen Kanesada strategically instructs them: “Let us first observe their movement”, but Ookurikara ignores him and strikes at the enemy.

After the fight, the rescued woman introduces herself as Lady Koshosho. According to her, an intimate of Murasaki Shikibu, this era of Heian-kyo seems to have been overcome by the fictional world of The Tale of Genji.

Under the guidance of Lady Koshosho, Kasen Kanesada and the others begin to investigate the imperial court, where they observe Hikaru Genji animatedly engaging in amorous talk with aristocrats that never existed in actual history. It was a famous scene from the Tale: Commentaries during a Rainy Night.

Having witnessed a scene that had never existed in any era, Kasen Kanesada and the others take stock of their current situation. This was a world where "history" and "story" were reversed.