For these two, I've always seen them as naturally being drawn away from the arena over time, which comes with an increase of risk. I would say they both desire more intense consequences of harm, and seek it mutually, but also aren't thinking entirely about how this could go 'too far'.

Going on a tangent (sort of) (it's related) but, I think of inklings on the whole as desensitized to violence, and lacking a complete understanding of their own mortality. They're recreationally popping each other all the time — there's just a lot of rules & structures in place to allow this — but it's easy to become so used to it as a baseline. Part 2 of what complicates this, is that inklings are quite resilient, able to withstand a lot on their body, with an impressive regenerative ability. Even without a respawner, you could come back from something near-fatal, I think the 'point of no return' is harder to cross.

While I would say Harpoon and Ruki are a little more contemplative than your average inkling, they are just stupid thrill-seeking teens. And the feedback loop of harming/being harmed is something euphoric, easy to lean into, as opposed to forging direct communication (which they are bad at.) It's a way to express passion and interest, without having to say anything... I think they can both start to feel as though their relationship simply doesn't need to be anything other than this. It feels so good, better than anything they've ever experienced, so they want to keep pressing the Feel Good button. Just as well, Harpoon is egotistical and greatly enabled by Ruki's complete submission to him, she will not balk at him as he bulldozes forward with her. It sets a precedent for worse treatment lol, as he can endlessly get away with doing, anything to her. And she'll allow it. And clearly like it. So, problem.

To get into specifics, I used to imagine them in arenas after hours, though in kind of derelict crevices, Behind the walls and partitions for the proper matches. But nowadays with Avvy, we've come up with a setting that fills this function; a building explicitly for 1v1 matches called the Fingerling Frontlines. It's supposed to be for young self-conscious sploons, it's a bit run-down, not so glamorous, as the town they live in (Whale Fall) is quite small in scale/population. (Nowhere near the size of Inkopolis...) They'd move here for privacy, renting out the space for hours, just to have intense matches where the only objective really is that Harpoon is going to pursue Ruki all about with his e-liter. There's no objective with like, turf or her retaliating; they have no need for that. Like this, Harpoon also doesn't have to shy away from doing things like, yanking her, pinning her to the ground, which would be totally illegal in a normal match. Using both his hands and the 'liter in various ways, trip her, step on her, pin her, drive the tank into her body, bash her head, etc. There's so much interplay at this point... and only a desire to push it further!!

This is when things get dangerous basically, as you start to get into... freely restraining and stringing her up, choking her... gutting her with a knife. Purposefully shutting down any respawners available at the place, for the purpose of drawing things out as much as possible. Again, she could live through a lot, they could really push the bounds of what is OK... I think when Harpoon 'breaks', it's a moment of passion, compulsion to do something crazy to her, like cut her throat, or continuously bash her head into the ground, or reach his hands into her body and squeeze her heart himself. It's mostly a 'with hands', very close-range feeling thing. I think beaks are quite sharp and he could rip her apart with teefers even, aourhh, many things... Ruki could bleed out and that's that...

I always imagine for Ruki it's more of a serene feeling, accepting wholly she is going to die.. Even if there was some primal panic beforehand, ultimately she accepts this as Harpoon's decision, of what to do with her life. She's happy to be given a sense of purpose... doing something for him. She's not able to worry about being missed. As for Harpoon, it's a lot more complicated for him, as it's... both unfathomably satisfying to the crazy possessive sadist brain (took her life, forever...) but also devastating, all that he couldn't do for her, all that he didn't know about her; it'll crash down upon him. Complicated feelings of remorse... What's wrong with him? (And yet not entirely able to regret doing it, and couldn't say he wouldn't do it again?? If he could.) It's rough. To get this far I just imagine they have not consummated, not kissed or nothin', a kind of tragedy that they couldn't get further in this. Harpoon does not last long after, taking his life, as a form of atonement & not leaving Ruki alone. Shinjuu vibes... Sometimes I think of him immediately offing himself, other times lingering and going through Ruki's apartment, belongings, and (depending on the circumstance) keeping her body. Any number of things. But ultimately he will die too. There's nothing for him after this.

Sad of course, but I think there's also ways Harpoon feels a kind of... poetic acceptance of this as an end for them, as a conclusion of their natures. Maybe it couldn't be more than this... I think in the end, it's better to have experienced this together, than lived life without her. Just one of many possible timelines.