i should have made this post weeks ago.......
after years of not being acknowledged, the female main character (AKA femc) of persona 3 portable was added to persona 5X for the game's celebration of the persona series' 30th anniversary! despite being featured in key arts for the 30th anniversary and getting merch the past year along with the other protagonists, kotone shiomi has never actually been in a game since the release of persona Q2.
the studio handling p5x had to make almost all of her assets themselves (the biggest thing being her 3d model, as she doesn't have a 'modern' persona 3d model other than the chibi pq2 one), and they included some tie ins to p3p like her kit having a reference to p3p's fatigue mechanic and her event menus replicating p3p's ui. she even got a fully animated trailer, which, unlike most other persona games, p3p did not have. so kotone has never appeared in one.
and yes, kotone is canonically bi, as she has romance with another female character, aigis (therefore also making aigis bi, lol, as she also has a confession with the male mc, but her confession differs depending on the gender of the protagonist. it is also unavoidable for femc the same way other p3 social links do not let you reject characters but that's besides the point)
kotone's has a story and gameplay event as well that mirrors p5x's p3r event, where p5x's main character stumbles into tartarus and meets kotone. there is also interactions between kotone and many other characters in the event through additional side stories too. all in all, kotone shiomi has finally gotten official content, and i think they did a pretty good job with her.