You decide to let your girlfriend do whatever she want with her avatar and only preoccupy yourself with your own. As a joke, you decide to make your avatar a mermaid, but not a too feminine one. That’s part of the joke, to turn "you" into a tomboy of a mermaid.
As soon as you switch your avatar gender, a lot of adjustments are made automatically to make it look more feminine. While you’re glad it feminized your face for you, very satisfied with that part of the automatic changes associated with the gender switch, you’re also pissed at how it immediately changed your hairs for very long ones and took away your (already meager before) muscles and made you very slender. Thankfully, you can still correct it.
Well, you have to batt your girlfriend’s hand away, before she could validate your mermaid avatar as it currently is. When she kept trying while you repeatingly stop her from validating your avatar in its current state, not listening to your pleas to stop, you reinitialize her own. She’s about to scream at you, but before she can you firmly tell her that you wouldn’t have done it if she hadn’t tried to intervene in your own avatar creation.
With that little interlude left behind, which made your girlfriend rather grumpy, (but at least she concentrate on her own avatar) you continue your editing work. First you give your mermaid avatar very short, and a bit messy, hairs. You keep them the same color as your current ones. You don’t change your skin or eyes color either. You also make your avatar visibly strong, not by making it look like a bodybuilder. She look more like a 3-way mix between an olympic swimmer, (should be expected of a mermaid) a martial artist and someone that naturally use their muscles a lot in their everyday life. You also make your avatar a bit taller, but not much.
Another thing that bother you, is how whatever software you run this avatar creation exaggeratedly inflated the chest of said avatar upon turning it female. You have nothing against big boobs, but only as long as they go well with the body they are a part of, and those two melons don’t go well with the athletic body of your mermaid, so you deflated them from F-cup to B-cup, before noticing how it deflated them a tiny bit to much, and turned them into C-cup instead. While you’re at it you also enlarge the hips, because the software might have been far too generous on the chest department, when it come to the hips it was rather stingy, to the point your mermaid almost looked like she had a man’s hips!
For the tail, you choose a shark-like one, and enter the advanced configuration for it. You end up with something looking like a blacktip reef shark for the shape, and while your caudal fin did have the eponym black tip, you select a motif more akin to the one on a tiger shark, but force the colors to grayish shades of blue. That’s when you notice the possibility to add bioluminescence to your mermaid, and do so. Said lights, only visible when it’s too dark around her to see anything around without the help of her bioluminescence, reproduce the "spot & interrupted/doted lines" motif of a whale shark on both her tail and her arms, with more spot on her forehead and even a single line of it under her eyes, that one line being underlined by a just as lonely doted line which then go down the side of her cheeks, follow the back end of her jawline and rejoin the doted lines on her arms.
It is finally time to choose clothes! You could have left her nude, but decide against it. You search something akin to a sport bra, until you see cloths that look to be either for a princess or a priestess of some kind, but look strangely good on your mermaid. (Especially after you adjusted the colors of that garment.) But you feel hesitant to keep it on her if you can’t explain why somewhere… Is there any place to enter a backstory in this software?
To your surprise, there is, and you start tapping on the holographic keyboard that suddenly appeared that your mermaid is a distant cousin to the imperial family of her nation, the merfolks being just as divided than their distant cousins from the surface, the humans. She is so far down in the line of succession that here is virtually no chance of her ever sitting on the throne. In fact, she mostly live the life of a commoner, the imperial blood in her vein the only reason why she’s required to participate in all ceremonials. In her country, a matriarchal nation, the empress isn’t just their ruler, but also the highest priestess of their religion, and anyone sharing even the slightest drop of blood with her is automatically made a priest too. Not that it prevent the most distant relatives to still have to find themselves a job, which they might be forced to quit in a blink to be sent as an ambassador to another nation of the sea, or even one on the surface.
After all, if merfolks can live in the deepest meanders of the oceans, they can just as well live near the shore. They can breath air as well as water. In fact, if they dry their tail, those even become legs so they can walk in the world of the surface. Naturally, the change isn’t as perfect as in the movies. The legs skin is still the same as when it’s a tail, the caudal fin being the only fin to disappear, turned into two feet. And at night, as long as the light pollution is low enough, their bio-luminescence activate.
Merfolks aren’t any less technologically advanced than humanity even if, living underwater, their technologies are very very different from what you see on the surface.
You precise that your mermaid, for her part, dream of becoming a knight of the realm, a dream she had been forced to put on hold for a time, forced to go to high-school on the surface to try an foster a better understanding and some diplomatic goodwill with one of the human nations, her welcome back ceremony the very reason she was currently in ceremonial garb. You even had that she can’t wait for the ceremony to end so she can search and reconnect with her best friend, whatever merfolk your girlfriend created. Her avatar would be friend with yours, right?
As soon as you validate, you have great difficulty to keep your eyes open, or even stay upright. Blackness envelop you as you feel yourself falling, but loose consciousness before you can reach the ground.
— – - – —
You suddenly find yourself in front of a group of real-life merfolk, clearly under water, and your body feel really strange. Looking down, you see a clearly feminine body under the garments identical to the ones you had selected for your mermaid avatar. In fact, connected to your now generous hips you can see her tail.