WARNING: The following contains spoilers for Rust-Eater Bisco Volume 2 of the light novels and possible spoilers for a potential Season 2 of the anime.
Rust-Eater Bisco, also known as Sabikui Bisco, is probably the biggest sleeper hit from the Winter 2021 anime season. The story focuses on a post-apocalyptic Japan where humans are fighting a cancer-like illness called rust. Season 1 covered Volume 1 of the eight that have been published so far. Volume 2 is now available in English, and it gives a greater idea of what Season 2 could be about.
It leaves off in a place where one might assume the story was going in the same direction it had been, with its characters fighting more against the government, which is attempting to get the cure so that they can monetize it. However, Volume 2 of the light novel introduces viewers to an even more elaborate world.
Season 1 of Sabikui Bisco introduced audiences to a world left over from massive destruction -- a world consumed by a mysterious and potentially life-taking disease called rust. Rust-Eater Bisco and Milo Nekoyanagi, the doctor from Imihama Prefecture, team up to find a cure for this devastating sickness -- an affliction that not only Bisco's father figure and mentor Jabi is struggling with but also Milo's sister Pawoo. During the season they go from unlikely duo to comrades in arms. There's the struggle against the government, a death, a resurrection and a fight against a big bad robot at the end.
Volume 2 of the light novel is titled The Bloody Battle with Lord Kelshinha. While the first volume dealt more with the world of rust and government interference, this one focuses more on religion and the corruption that can be found within. The religious sect calls themselves the Rust Speakers and is led by Kelshina, the legendary immortal monk who’s said to be over 200 years old.
The story opens with Bisco and Milo in the holy land of Shimane when they come across Kelshina, who is harvesting organs for Lord Mashouten, the sect's god. Bisco and Milo heroically save a child who was brainwashed into thinking that giving her organs was a necessary spiritual offering. Once free of the temple, Milo examines her and verifies she has extreme mental trauma. This provides a further glimpse into the story after they’ve learned from a group of Rust Keepers about the sect.
Because the Imihama Prefecture has called for Rust-Eater immigrants to come to live in the city, Bisco and Milo run into some of Jabi’s old friends, who are on their way to the city in which they will be welcomed. There is a brief hello and then a discussion about immortality. Bisco is surprised to learn that it’s not as uncommon as he thought -- Rust Keepers like Bisco don’t believe in a singular god, only that everyone has a god inside them. That is why they choose to do the right thing and listen to the voice within.
Long ago, the Mushroom Keepers had a god called Lord Kusabira, but Kelshinha from Shimane burned the temples and shrines. When learning that Kelshinha was an immortal monk, Bisco and Milo became interested because of Bisco’s condition. When Bisco was resurrected, he also became some type of immortal who is part human, part mushroom. Bisco isn’t all that keen on being immortal -- he wants to grow old and die with his partner Milo, and he can’t do that unless he finds a cure for his condition. Volume 2 of the light novel answers whether he can be cured, as well as puts him up against Kelshina, who steals his stomach and gives him only five days to live.
There will be more characters to look forward to in Season 2 besides just Bisco, Milo and Lord Kelshina. Two others are introduced that play a significant part in the story. First is Amli Amlini, who is described as a cute girl with a glass eye who lives at the Six Towers of Izumo. She's a shaman who is studying Amrit healing and has mastered a sutra for sucking out the rust. Then there's Raskeni Jau, Amli’s teacher, and a monk who's fought against Kelshinha and now works behind the scenes of the Six Towers to keep peace and order. This character is knowledgeable about spells and will likely lead the story into more magical territory. Previously, science was the key to this world, as was shown by Milo’s experiments and finding the cure for rust.
So far there has been no official announcement that Season 2 is in the works. However, knowing that there is plenty of source material from author Shinji Cobkubo to go from gives fans hope that Sabikui Bisco will be returning. Common predictions for when it will premiere are either late this year or early 2023.