Chapter 53 of the Jigokuraku manga.
Feeling in no mood to examine the Dōshi after finding out about the death of his comrades, Fuchi decides to set him free. He then walks over to the cave Sagiri, Yuzuriha and Mei are in. Sagiri informs Fuchi that Mei is feeling ill and requests that he make some medicine. Fuchi agrees to help but demands that Mei tell them everything they need to know about herself and Lord Tensen. Meanwhile, Gabimaru sits outside and makes a request to Gantetsusai, Tōma, Shion and Nurugai to help him train who to utilize Tao. Tōma starts off by attacking with Gantetsusai's sword given to him. Gabimaru focuses on sensing the movements of his Tao and dodges his attacks. Gantetsusai then comes in to make his attack on Gabimaru. Gabimaru uses his Tao to sense Gantetsusai's weak spots in his Tao and strikes, causing him to feel discomfort. Nurugai then jumps in and tries attacking. Gabimaru grabs Nurugai and swings her to push the others back. During his fighting, Gabimaru believes that the key to defeating Lord Tensen is to use their own Tao against them. Nurugai becomes impress with his skills and finds him capable of fighting Lord Tensen. However, Gabimaru believes he still needs more time to improve. Gantetsusai states that he is about to get serious and manages to strike Gabimaru. After interpreting Mei's words, Fuchi explains to Sagiri and Yuzuriha that the island, the monsters, and Lord Tensen were created from a Hōshi in his attempt to research ways to achieve immortality. From his experimentations, the Hōshi created Lord Tensen from Human and Plant Tao. After Yuzuriha asks what was their purpose in living on the island, Fuchi explains that the Tensens have been practicing the Inner Ways of Tao, which is meditation, and Outer Ways of Tao, which is making an elixir, to achieve immortality. Hearing this, Yuzuriha and Sagiri become shock to realize that the elixir does exist. Fuchi tells them of the prototype elixir known as Tan, a potion created from harvesting and extracting the Tao of humans in order to expand the Tensens lifespans. Knowing this, Fuchi tells them it is possible to kill Lord Tensen if their Tao is depleted. Yuzuriha then questions why they are going further with their research since they have already created Tan. Mei answers saying that it was possible that Lord Tensen was following the will of their master, Xu Fu. Fuchi explains that Xu Fu, also known as Jofuku, was a Hōshi and servant to the emperor of the Qin Dynasty, who journeyed off to research the secrets of immortality 1,000 years ago but eventually came to an end once he entered Japan. Sagiri then becomes frighten hearing the possibility that Xu Fu might still be alive on the island.