WARNING: The following contains spoilers for Rust-Eater Bisco Episode 11, "I'm Bisco!," now streaming on Crunchyroll.
The fight against the Tetsujin in Rust-Eater Bisco continues to be arduous as it lays waste to everything in its path toward Imihama. While Milo does his best to channel Bisco's strength to defeat it, it may not be enough. Fans will be left wondering if the titular lead's remarkable re-appearance is real or of a more spiritual nature, but it's nevertheless proof of not only how important Bisco is to Milo, but how necessary he is to the salvation of Japan.
Jabi and Pawoo do their best to assist, now with Tirol and the entirety of the Imihama Watch joining the battle in support. Still, Milo quickly and continuously ends up taking on the Tetsujin alone, not unlike the way Bisco would take on Kurokawa. Milo channels Bisco's strength and determination to help him get through this seemingly impossible battle, with Jabi noting how much like Bisco he's become, almost dangerously so. As the group arrives to save the children of Tetsujin Town, even Nuts, Plum and Kousuke are stunned by Milo's eerily uncanny demeanor in battle -- as well as Bisco's absence.
Over the course of the battle, Milo makes clear that the Tetsujin is following Kurokawa's will and is perhaps an embodiment of the villain altogether. Having risen out of the molten rust where Bisco and Kurokawa died, it's not entirely impossible that Kurokawa's body -- and consciousness -- would have been absorbed into the Tetsujin.
While the behemoth monster is a created weapon, it becomes clear in Episode 11 how little people actually know about it. Jabi refers to it as being akin to a death god because of its unfathomably destructive power, and the Rust-Eater mushroom a death-god eater. Even Tirol tells Pawoo that the Tetsujin and its manual are entirely incomprehensible to anyone who isn't already familiar with how it's built.
Bisco's death may have been astonishing to fans, but Rust-Eater Bisco handled it well through making Milo embody Bisco's ideals and promising to carry out his mission. The depth of their bond has been at the forefront as Milo faces off against the Tetsujin, but Episode 11 brings an even larger surprise: Bisco's return. Though it very well could be metaphorical, the fact that Milo finds Bisco's goggles in the Tetsujin makes Bisco's real-life return possible given the goggles were still fully intact.
While it hasn't been entirely explained just how Kurokawa and the Tetsujin are one in the same, the mystery means Bisco could have possibly survived. Further muddying the possibilities, though, are his missing arm -- having been destroyed by the Rusting -- appearing newly intact and glowing red. However real Bisco may be, he continues to be the helping hand Milo needs in this crucial moment, providing an essential second wind.
The Tetsujins nearly wiped out all of Japan in the past with their destructive power and proliferation of the Rusting. With Japan still struggling to recover, this second battle may very well be the one that ends it all, especially with the obvious difference in size and power between it and its main opponent Milo. Before Milo goes off to face the Tetsujin again, he and Jabi discuss how the mushrooms have evolved alongside the rust and the potential power they have in reversing all the damage. This hope has been the motivating factor all along through Rust-Eater Bisco, but they seem no closer to unlocking the power of the mushrooms, Rust-Eater or otherwise, to make a large enough difference.
However futile the battle may seem -- and how dangerously close Milo is to sacrificing himself to succeed -- Bisco reappearing is a continued sign of hope. Whether he's come back from the dead or is simply a manifestation of Milo's grief and struggle to survive, the presence of his strong will could very well be what tips the scales to save Imihama, and the rest of Japan, from a second rust-filled apocalypse.
