I was rereading a bunch of stuff from 'Submas' week and it struck me how the majority of fics really zero in on this one core thing: separation. Like, the twins are practically a single entity in canon, fused at the hip with their whole battle double act, so naturally fanfic writers see that and go 'okay, but what if we took a crowbar to that?' A huge chunk of stories are just variations on them being torn apart, either physically—Ingo getting yeeted to Hisui in 'Legends: Arceus' was basically canon handing the fandom a gift-wrapped plot generator—or emotionally, through some kind of misunderstanding or trauma. It's not just about the angst of missing someone, though there's plenty of that. It's about exploring identity when half of your foundational partnership is gone. Who is Emmet without the person who shares his literal catchphrase? Who is Ingo when he can't remember the other half of his own soul? The fics that dig into that, the ones where Emmet meticulously searches or Ingo has these vague, aching memories of a smile he can't place, they get at something really specific about codependence that isn't necessarily unhealthy but is utterly fundamental to them.
What's maybe more interesting are the quieter stories that assume they're together. A lot of those are domestic fluff, sure, just cute slices of life running the Gear Station or making curry. But the best ones use their contrasting personalities—Ingo's more reserved, rule-focused nature against Emmet's blunt, cheerful intensity—to explore how they balance each other. I read one where Emmet was struggling with a bureaucratic problem and Ingo just methodically laid out the regulation that solved it, and it was framed not as boring but as this deeply loving act. Their dynamic is less about big romantic declarations and more about this seamless, operational synergy. Even the shipping fics, whether you read them as romantic or not, often focus on that synergy being tested or deepened. It's less 'will they/won't they' and more 'how does this unit function, and what does it mean when it's compromised?' The fandom has built a whole language around them, using train metaphors and station terminology, which feels less like a gimmick and more like the natural extension of characters who live and breathe their roles.