Even while Knights of Sidonia, Vol 9, Ch 43 is overtly establishing a parallel in the relationship between the Human Knight Tanikaze & Gauna Hybrid Tsumugi by making a callback to my favourite vignette from Biomega Vol 5, Ch 53 it puts such a huge smile on my face. While Nihei's Digital Knight dynamic was first established with Mensab as the Animus of Toha Heavy Industries & Seu as her broken warrior with its own tragic struggle in Vol 3, Log 23 of BLAME!, I always felt that Biomega having Higuide & princess Irungorunuruka's story took that into a place that made it feel truly iconic by allowing it to exist entirely on its own. It's just happening suddenly in the midst of everything else, while also borrowing the name of a different side character ally in BLAME! to have a familiar link, but it's SO unexpected and just perfectly delivered.
Their story also feels like it has continuing echoes in the primary conflict in Aposimz which involves going to confront a seer in control of a region oppressively ruling over everyone with a hidden tragic backstory, and in how the ongoing Tower Dungeon is following a story with a captured princess held captive in a tower that only descends periodically. It's nice seeing nods to how this one little side story still holds so much weight, and the pieces of it that stick around in different forms even when it's not just being shared again.
I also find the Knights of Sidonia film version interesting because it's seemingly all actually redrawn rather than taking the extant panels from Biomega, and has little subtle differences like using "Tanno" as Higuide's name since it's the word the people of Iyaak use for "foreigner" since he falls from the sky, but princess Irungorunuruka learns his actual name, and is what she calls out at the very end in the original.
Just to showcase the panels from the original where only the dialogue is shown, as well as the double page spread of Higuide's attack against Chaidorin:
I go back and reread this one chapter in Vol 5 of Biomega all the time, because it's just perfectly contained as a standalone story that gives your mind everything it needs to be utterly captivated in an elegantly succinct delivery of only 30 pages.
You literally could just read that chapter with zero context at all, and take away all you need. Having all of the prior context from earlier in the manga also makes it especially fascinating how you'd never expect things to end up there, and that you never find out anything else. I think about it constantly whenever I'm inevitably drawn back into diving into revisiting the worlds of Tsutomu Nihei's manga, and wanted to just gush about it a little bit.