Ok so the terms "cis" and "trans" come from Latin suffixes used in organic chemistry regarding isomers. Basically if functional groups are on the same side of the carbon chain, they are "cis" and if they are on opposite sides they are "trans." We also apply those suffixes to gender, and although that really doesn't 100% make sense given what the suffixes mean (e.g. "same side,"), it's what we use.
So they called the gender change isomerism. ISOMERISM. Aka organic molecules with the same formula but different structures. THIS IS TOO MUCH ORGANIC CHEMISTY WTF STOP IT. THAT DOESN'T EVEN MAKE SENSE HNNNNNG...
Ok nerd rant over.











This is the author of May Belongs to Me (aka that webtoon about a guy kidnapping and keeping a guy but kind of also thinking he's a cat.)
Same artist but a different author.
I feel better about this then.