Accardo's Descendant (アッカルド の 子孫, Akkarudo no shison) (thus far unnamed) is a young man who becomes invested in the events of the 1700s after discovering the accounts of his ancestor Jean-Pierre Accardo in a hidden chest.
Born sometime between 1974-1983, the Descendant grew up in Lotto Valentino, Italy towards the end of the 20th century. At some point his parents died in an accident, leaving the Descendant to squander his inheritance by traveling around the world.
Several years later in 2003, the twenty-something young man returns to his hometown as he is running low on cash. He heads to the family house on the city edge, and finds a chest the size of a small bathtub in the attic. He has never seen the chest before, but recalls that his ancestor was a famous poet who'd written many plays, and wonders if perhaps the chest contains Jean-Pierre's valuables. The situation has a feeling of adventure to it, causing the Descendant's heart to race. He is soon disappointed when he opens the chest and discovers "hundreds of thousands of pieces of parchment," which by appearance alone don't promise to be worth much money. However, it is possible that they are plays or poems by Jean, which would likely be worth money to a museum or library. "Shamelessly considering using his ancestor's name to make profits," the young man skims through the writings, which are written in an 'archaic style' three-hundred years old or so. However, since the Descendant had been fond of reading classics as a student, he could 'barely understand' the content. He ends up reading the entire accounts, visiting the Third Library several times in the process of deciphering Jean's writings.
Once he reaches the false ending of Jean's accounts (in which Monica is implied as alive and the overall 'ending' happy), the Descendant (who does not care about the immortality mentioned within the memoirs) is moved by his ancestor's 'noble character' and offers up a prayer, hoping that Monica and Huey had indeed been able to live their lives out in peace.
However, he is bothered by one thing: the inside of the chest looks shallower than the outside. He decides to take the box apart, and finds another bundle of parchment in a secret compartment (presumably the chest had a false bottom). He reads those too, and discovers the real truth that Accardo had kept hidden, such as Monica's death. In his final letter, Jean states that he intends to commit suicide, and the Descendant, wondering if his ancestor had done just that, cycles to the Third Library to consult the many books on Lotto Valentino's history. After three minutes, he learns that his ancestor had lived a long life, dying at the age of ninety-eight.
The Descendant curses his name, calling him a coward. But he can't help but harbor doubt, wondering if he would have been able to commit suicide had he been in his ancestor's shoes. Now, he no longer thinks that the accounts are fiction, and he proceeds to read through the library's history books, learning about the Avaros, the Boroñals, the Dormentaires, and the great fire that swept through Lotto Valentino in 1710. As he reaches a passage about the 1711 conflict against the House Dormentaire, he is approached by the library manager, who recognizes him as having visited the library several times prior and asks him if he needs anything. The Descendant wonders if this man is Dalton the immortal from Jean's memoirs, but since the man's right hand appears to be real (he does not have the hook mentioned in the accounts) the Descendant dismisses the thought. Dalton informs the Descendant that it is closing time and that he will put away the books for him.
Now fully invested in the events of the 1700s (and now also in debt due to his research) the Descendant visits a maritime museum on the North American east coast, where the Advena Avis is currently on display. He and other museum patrons listen to the curator recount the history of the ship, and when the curator asks if there are any questions the Descendant raises his hand to ask if there are any surviving researchers from the 'scientists' aboard the Advena Avis. When the curator replies that there are, the Descendant asks to take a look at them. The curator tells him to fill out an official request form and to speak to one of their archivists. The Descendant goes to the museum's archivist manager, who at first refuses to disclose the research notes. He changes his tune when he learns the Descendant's name (presumably his surname is Accardo) and asks him if he is a relative of Jean-Pierre, saying that the museum had sent its own researchers to Lotto Valentino but hadn't learned much about the Advena Avis through their own efforts. As for the notes, they've been keeping tight wraps on them because they might put Lotto Valentino under scrutiny, such is the importance of their contents.
The manager takes out a journal from the Advena Avis, and points out a certain page to the Descendant. He says that the museum believes it is contains the logs of one of the crewman aboard the ship. They'd initially thought they were mere travelogues, but the paper quality is unusually expensive. A report, at best. The manager goes on to mention the more outstanding point - that the journal contains words like immortals, demons, and alchemists. The Descendant interrupts him to ask if the journal mentions an immortality elixir or whether or not they became immortal. At this, the manager is excited and asks if Jean-Pierre had left Accardo a record of some sort. "Why do you think so?" asks the Descendant. The manager points to the name Jean-Pierre Accardo on the page he'd opened before, and says that a few of Jean's acquaintances were aboard the ship, referring to other logs that were recovered from the ship itself. At this, the Descendant is interested; the manager continues by revealing that one of the passengers had murdered many people aboard the Advena Avis. They continue talking about the unusual circumstances surrounding the ship's departure and its passengers, and the manager eventually recounts to the Descendant the entire story of the 1711 incident involving House Dormentaire and the Mask Makers.
Once he is finished, he returns to the subject of Jean-Pierre, and points out the incongruity that although Jean hadn't been in Lotto Valentino at the time for "personal reasons," he still managed to turn the 1711 incident into a play. This is the reason he is interested in whatever knowledge the Descendant might possess, because the museum currently cannot figure out how Jean had been collecting the pertinent information -- although, come to think of it, he had a connection with Dormentaire spies according to their files. He asks hopefully if the Descendant knows anything that would be useful. The Descendant is about to insult his ancestor's name when their meeting is interrupted by the museum receptionist, who informs the manager that the FBI is requesting access to the Advena Avis research material. The Descendant is there to see the material collected by FBI Agent Jessica Sullivan. He arranges to have another appointment with the manager in the future, and leaves the museum.
As he walks down the sidewalk, he overhears Victor Talbot shouting at Jessica from inside a parked car. He recognizes Jessica (who is sitting in the driver's seat) as the FBI agent from before, but his thoughts are interrupted when he bumps into a heavily bandaged woman who looks twenty years old. Her companion (Lucrezia de Dormentaire) apologizes on her behalf, and the Descendant, who is taken aback by Lucrezia's beauty and seductive personality, ends up walking away "as though in lieu of an apology."
- In 1935-B: Dr. Feelgreed, Dalton Strauss reminisces about his past to an unnamed individual in 2003, discussing how he and nine of his students (including Renee Paramedes Branvillier and Archangelo) became immortal. It is clear that the unnamed individual previously knew about immortals and Dalton's prosthetic. In 1935-C: The Grateful Bet, an unnamed mortal individual approaches Phil in 2003 to ask about Szilard Quates. During their (one-sided) conversation she suggests that he seek out Szilard's Descendant Bild Quates or Szilard's devourer, and she talks about Szilard's preoccupation with homunculi and knowledge.
- It is very likely that the individual in both these passages is not only the same person, but in actuality the Descendant, who has taken a very active approach to his research in the 1700s timeline: he has traveled all the way to visit the Advena Avis in an American museum and visited the Third Library repeatedly, among other activities.