The Squids and the Octarians are still at war...
now i'm legit curious about Marina's backstory and her constantly worried look.
Is she a POW?
I've theorized for a long time that Inklings and Octolings aren't "inherently" opposed (think kind of like how in the Paper Mario series, there are a lot of Koopas and Goombas who are just passive good guys). The scrolls in Splatoon 1 showed that Inklings and Octolings used to live together in harmony, but something happened along the way that exiled Octavio to Octo Valley where he controls primitive Octarians for his own nefarious purposes. The credits for Splatoon 1 also show an image where some Octolings get along with Inklings.
So my theory with Marina is presumably she knows many Inklings view Octarians and Octolings negatively and that's why she's a lot more submissive/anxious, but Pearl maintains a gung ho attitude to keep her motivated like a big little sister. Maybe she's an idol because she wants to bridge the gap between Inklings and Octarians, kind of like a positive icon.
I guess you can read into the class/racial divide undertones in there somewhere.