Jigokuraku Extra Chapter is an omake-chapter included in Weekly Shonen Jump Issue #36-37 of 2018.
Summary[]
After assembling members from the Yamada clan, Aoki and co. explain to them their mission of watching over exiled criminals while they embark on a journey to a certain island as decreed by the shogun. Aoki further explains that the island has been said to be "Shinsenkyō" and holds the Elixir of Life, which is desired by the shogun after he had sent sixty men to retrieve it. However, only a few had returned back alive and were mysteriously transformed into blooming humans. The shogun then decided to go a different route by sending death-row criminals with superhuman abilities and reward one of them with a pardon if they were successfully in their task. Later, the Yamada Asaemons board the ships with the death-row criminals as they depart to the island. Yamada Asaemon Tenza asks Yamada Asaemon Sagiri if she was feeling okay with departing to a dangerous island and then hears Yamada Asaemon Eizen's warning that they would also have to be wary of the dangerous criminals as well and points towards Sagiri's assigned criminal as an example: "Gabimaru the Hollow". Sagiri states that she is fully ready for what's to come and is prepared to execute her criminal if he were to make a wrong move. In an expected turn of events, Aoki is stabbed from behind by one of the samurai, who explains that he and his men will kill all the criminals onboard after viewing the trust the shogun placed on the criminals as unforgiveable. Aoki then calls on the Asaemons to protect the criminals since they can not fight back with their hands tied. However, each one of the criminals are shown being capable of defending themselves easily due to their high reputation as being dangerous individuals. Seeing as how he is merely sitting by himself, the samurai target Gabimaru but have their blades broken upon making contact with his body. Gabimaru says that he is not ready to die, due to certain circumstances, and kindly asks that they don't proceed to attack him since he does not wish to kill them. One of the samurai is then stung by a strange butterfly that was hatched from the blooming man that had survived the previous expedition and starts to attack the other samurai uncontrollably. Sagiri defends Gabimaru from the samurai, since she was previously ordered to, and refuses Gabimaru's request in undoing the bindings on his hands since she would be breaking the rules. Gabimaru notices that the samurai is acting strange judging from his aroused face, the vines growing from the back of his neck, and his body being uninjured from Sagiri's attack. Having no chose, Gabimaru sets himself on fire and incinerates the samurai. After Gabimaru points out the proof that the criminals were useful, the leading samurai berates him, saying that they are all fated to kill one another and that only one of them can be rewarded with the pardon if the elixir was retrieved. Gabimaru becomes unflinched by the samurai's words but reacts after the man threatened to target his family by setting the ship on fire. After hoping on board the same boat Sagiri is in, Gabimaru wonders as to what happened to make the samurai act uncontrollably. Though he had realized the strength of the criminals, Aoki was unsure of the success rate of capturing the elixir. After a few criminals and executioners had made it to the island, Gabimaru charges and attacks a group of giant monsters with a vow to return to a certain woman no matter what kind of hell he may face.