Nina is one of the 2nd-generation child units the player can recruit to their army once her father, Niles, has an S-rank with another female unit in your army. As a character, she is known for her obsession with men being more than friends (as shown below with support dialogue text). Because of this, many fans have associated her with loving yaoi (Japanese boy-on-boy love).
Corrin: No, of course not. But now I’m curious… What have you been up to, Nina?
Nina: Oh, nothing interesting at all. Nothing even worth talking about. I suppose if I had to say SOMETHING, I would say I was…people watching.
Corrin: People watching?
Nina: Yeah! Like, see that guy over there? The one dripping with sweat from practice?
Corrin: Yeah, looks like he had quite a workout.
Nina: And then over there, there’s a guy tending to some horses. What if those two guys met up…like, for a cup of tea? Wouldn’t that be splendid? What would they talk about? Would they become fast friends? Or something more…
Corrin: Something more? I’m not sure I understand.
Nina: Oh, well, never mind that, then! Just imagine a good, old-fashioned friendship. But then one day they find themselves in the middle of an intense staring contest… Hee hee!
Nina: All right, then. Let’s say—hypothetically, of course—that I love spying on men. And not just any men. Men in close relationships. Men who are best friends. Weirded out yet?
In the world 1 hub, if you play a special melody on the medusa, you can unlock a hidden level where you can meet a mermaid, a being that is a mix between a human and an octopus. She tells you that you will always meet people that don’t fit inside any box, that they are valid, and that her cave is a safe space.
Chihiro Fujisaki is one of the teens trapped inside Hope’s Peak Academy and forced to play the Killing Game. In the second chapter of the game, it is revealed that Chihiro is biologically male and dresses as a girl to deal with an inferiority complex. Chihiro was bullied as a child and told that he was weak for a man, resulting in him deciding to dress up as a girl as a way to be socially accepted as “weak”.
Many fans have speculated whether Chihiro is a trans character or not, but canonically, it seems that Chihiro identifies with the gender he was assigned at birth according to a conversation Chihiro has with Makoto during “School Mode” (found here) During the second chapter of the game, there are trans shock “she was a he?!” tropes played up as the rest of the cast find out about Chihiro’s secret (found here).