Tell us about that Splatoon oc!
Unfortunately they (as an individual) do not yet have much lore. Still working on a name and personality and such. However!
As a Cuttleling, they are a nerd with anxiety. Obviously not all Cuttlelings are like that since it is an entire species, but they do tend that way, especially culturally. They believe in cool tech for its own sake and for the sake of bettering everyone's living conditions. And also fighting off Salmonids when they attack (Salmonids find Cuttlelings to be very tasty).
This particular individual is part of the subset of Cuttlelings that think making a proper first contact with the nearby Inkling community (and therefore revealing their existence as a species) is probably a good idea. Probably. Unfortunately, as with most others who share their perspective, there is a pervasive fear that if things go wrong the Inklings will force all the Cuttlelings underground like they did the Octolings and it'll be all their fault.
(For this reason, all actual Cuttleling contact with Inklings is in the form of spies who watch Inkling technological development to see if anything appears that could be useful to Cuttlelings. The fact that they've been spying on them for a while now only adds more anxiety about first contact.)
(The spies would all be very easily detected if anyone knew Cuttlelings existed because despite being very brave for Cuttlelings, they still appear to Inkling society as weird social recluses. Everyone's just too polite to comment on it because hey, another squid's obvious neurodivergence is none of your business.)