Becoming Eden [It’s me I’m trees] by Lenipez
Do you know what a Salmon is?
Sometimes being a plant means doing nuclear fission through reverse photosynthesis.
Sometimes it means tasting colors and reading minds.
Sometimes its about realizing your old flame's son is a journalist now.
Sometimes its about drinking vanilla extract and wanting to claw out of your skin.
Vash doesn't have the words exactly for what starts happening to him after Knives played a frequency into his Gun at Jenora's rock. He can feel the math of it, the shape of it, but the words escape him for the next 300k. This Fic is about psychically conjoined twins, nuclear fusion, falling in love with the sun, becoming a salmon and discovering what Ao3 can do with ascii art. It's a Stampede canon divergent fic that crashes off the rails at episode 4 with plant head canons I came up with while watching 98 years ago...and some how I caught a lot of dodge balls. Its also a time loop story that incorporates elements of Trimax and 98, but that's a spoiler for part 2.
19 chapters (and some appendices), ~81,000 words, Complete w three sequels (the latest still being regularly updated. Don’t know why it’s still marked incomplete.)
This fic is great! Really weird alien biology, experimental style, really impressive use of the medium (which only escalates in the sequels). Also Lenipez is great at unfolding characterization.
If this fic is too much commitment, you should also check out the works in zir Vashwoodweek23 series, for some shorter (and less experimental) samples.
You probably do need to be familiar with at least one iteration of Trigun canon to understand this. It cleaves most closely to the world of Stampede, but even then its relationship to the timeline is pretty vague.