The Notorious Bored Samurai 4

Mondosuke ventures alone into the land of Nagasaki. There, he encounters young lady named Kinue, the daughter of Nagasaki's former magistrate office constable, Shusuke Kaneko. Monsuke has received information that Shusuke has been captured on charges of embezzlement, prompting him to head to the magistrate's office. However, the arrival of the Chief Inspector, Shigehide Ogiwara , obstructs Monsuke's actions.

The Satsuma clan conspires with key figures in the shogunate to overthrow the government. However, the head inspector, Naito Yamashiro no Kami, cannot find the sworn statement of rebellion and takes responsibility by ending his own life. This deeply affects Mondonosuke Saotome, who was close to Yamashiro no Kami and who is known for his restless nature. Seeking an audience with Shogun Tsunayoshi to request a view of the sworn statement, Mondonosuke Saotome is granted permission to go to Satsuma. He sets off on this journey accompanied by Sasao Kinai and Yamashiro no Kami's sister, Shizue . However, on the way, they are attacked by a group of mountain monks. Mondonosuke Saotome manages to repel the monks in a brawl but becomes separated from Kinai and Shizue. Afterward, he encounters a mysterious woman named Oren, and with her guidance, he finally arrives in Satsuma.

One night, Sawatari Shusui saves a geisha named Osode from a ninja attack. Osode's mother is said to be carrying the child of the shogun, Tsunayoshi, and has hidden herself on Hachijo Island. Shusui heads to Hachijo to verify the truth. Meanwhile, Shusui had heard from Tsunayoshi that he was planning to appoint the Kofu Chancellor, Tokugawa Tsunatoyo, as the next shogun, but Sumi's father, Makino Bizen no Kami, whose daughter was pregnant with Tsunayoshi's child, was planning to have his daughter's child ascend to the shogunate and seize real power. Amidst all this, Shusui, along with Osode and his servant, Sasao Yoshinari , sets foot on Hachijo Island and meets Tsunayoshi's son, Kotaro, who was born to Osode's mother. But then a group of ninjas attacks.

Sawatari Shusui saved Princess Hiroko of the Konoe family, who was about to be married to Tokugawa Tsunatoyo. However, Hiroko, a tomboy, disappears. As someone is after Hiroko's life, Shusui pursues her whereabouts... Meanwhile, Sasao Yoshinari and Shusui's sister, Kikuji, who were following Shusui, meet a young man and Kikuji is captivated by him, but they do not realize that he is Hiroko in disguise as a young man. Shusui is set to search for Hiroko with her attendant Orui, but that night they are attacked by a group of ninjas at their inn.

Sawatari Shusui was told about 7,000 ryo of buried gold by Osuke, who claimed to be a princess of the Fujiwara family. Shusui speculates that powerful people in the Date family and the shogunate are planning to overthrow the shogunate using buried gold and gets excited about a major national crisis. He gets separated from Osuke due to interference but with the help of his sister Kikuji and others he tracks down Osuke's whereabouts. He then realizes that Osuke is not from the Fujiwara family but is actually the daughter of Edo elder Itakura Shōken who has been confined under the pretext of an epidemic disease. Having promised to help Osuke, Shusui goes up to Edo Castle and advises shogun Tsunayoshi not to visit Nikkō Tōshō-gū Shrine which has been restored by Date family because "evil spirits are attached". However, Tsunayoshi is furious and orders him to stay under house arrest.

The great merchant of Kaga Daitokuya , had taken control of the domain with his wealth and by holding onto the weakness of Lord Maeda Tsunanori , and was planning to rule over Japan as well. In order to free the lord from evil spirits and monsters, Sawatari Shusui heads towards Kaga Hyakumangoku. On his way, Shusui helps a girl named Oyumi who was about to be bullied by a ronin. Oyumi claims to be the daughter of Daitokuya, but she is actually the daughter of Lord Maeda Tsunanori's concubine. Daitokuya, who had taken control of power by raising Oyumi on behalf of Tsunanori who could not make it public because of his legal wife, was secretly storing weapons and ammunition and was pressuring Tsunanori to sign a letter of rebellion.

The two ronin that Sawatari Mondonosuke saved were secret envoys from Ryukyu. They could not stand the tyranny of the Satsuma clan and were trying to appeal to the shogunate. But they were captured by someone afterwards. Mondonosuke’s boredom bug started to stir… Mondonosuke rescued the two who were imprisoned in the mansion of the chief elder, Okubo Iga-no-kami , as well as a senior official, Mamoru, and his niece, Reika , who had also escaped from Ryukyu. The Satsuma clan hired Wakura Juro to assassinate Mondonosuke through his daughter O-Ran, who is a spy …

The one who hurriedly ascended the castle upon hearing news of Shogun Tsunayoshi's illness was Saotome Mondonosuke. However, instead of an illness, he was prompted to consider a marriage proposal with Yaehime, a daughter of the Date clan. Yet, this was merely a pretext, as he was requested to investigate the truth behind the rumors of rebellion within the Date clan. Mondonosuke, who took on this task to stave off boredom, accompanied by his retainer Kinai, departed for Mutsu, following the procession of Yaehime returning to her home province. However, remnants of the Toyotomi faction, already plotting the overthrow of the shogunate, had gathered under Kii Koya Bunzaemon…