I've had Rekki around as a character probably going on twenty years or so, so she's evolved a lot over time, but you can still generally recognise a lot of the key elements of her design even in the oldest drawings. She always short, has straight eyebrows, that distinctive spikey fringe and hair the colour of a British postbox. She's also a fashion disaster in every. single. version.
This is the oldest ever drawing of Rekki. In this one she and Subo were supporting characters in a different story. I realised quickly they were the best characters and the story ought to be about them.
Here's a general overview of Rekki's development over the years after that as the protagonist of "Fan Dan Go" which got rebooted a bunch. You can see how the shape of the sword changed from this.... I don't know it looks like a crappy western take on a ninjatou or something... to a bit choppy thing probably inspired by Bleach, to Rekki's iconic and silly "rectangle with a hilt"
Rekki is a character who changes clothes. So next arc she will have a new outfit, but I wanted to continue from Fan Dan Go by starting her out when she made her adult debut in the chest high red sailor pants and cropped jacket, because I think of that look as kind of "classic Rekki", and it was the outfit she started Fan Dan Go in, so I liked the idea of it being her first outfit as an adult in Errant.
The bottom image is of course the old thumbnail for Errant, but because it was drawn before I'd done many updates on that comic, so I'd actually only drawn Rekki as a 14 year old in an orange puffa jacket when I drew this one. When she did finally get the timeskip and wear it, I did make a few changes mostly to the colour scheme to make her more cohesive. Oh also she wears shoes that aren't from 2002 now:
