Brand new characters?! Not just one, but two brand new characters!
I've had some ideas every now and again that require Miyuki to have coworker(s) at the gym, so I've given her some coworkers. And you're seeing them here first.
Please meet Vanessa (L) and Kelly (R). I haven't decided on last names for them yet.
I haven't decided yet, but I'm thinking I want Vanessa to be a fifth ninja girl. She's tough when she needs to be, but in general very funloving and easygoing. If she's a ninja, then she'd probably be part Brazilian (Brazil has the largest ethnically Japanese population outside of Japan; if there are ninjas in the US, there would be ninjas in Brazil).
Kelly is a sweetheart who really wants to motivate people to reach their fitness goals. She's a genuinely kind person, and in some ways innocent - she's from a suburb somewhere and has a very conventional worldview and in consequence disbelieves a lot of what goes on - ninjas, mummies walking around, hauntings, Aztec Serpent Gods. Rationally, these things are not really possible. When she actually sees a mummy walking around, she just assumes it's big city weirdness. It's possible she's just not that bright, too.
Since they're all young women around the same age, Miyuki, Vanessa, and Kelly naturally all hang out together at work - they're jobs as trainers have a lot of down time - and sometimes outside of work as well. Since they share a locker room, shower together, and use the sauna together, they will casually strip naked in front of one another. Overall, though, the other girls are more modest than Miyuki (which isn't hard, really); when hanging out in the locker room they will usually put their clothes back on after a reasonable interval. So if an adventure suddenly starts at the gym it could be a naked adventure for everyone, or a CFNF one for Miyuki.
Gym Miyuki, for reference:
https://www.deviantart.com/penguin-commando/art/Miyuki-s-GPVRG-3-Gym-Trainer-Ninja-860086332
So who takes care of her Vivastra Yoga class when she's out sick?
Enjoy,
-D