The dynamics between Ichigo and Rukia have this incredibly solid foundation in mutual life-saving and respect that I think sometimes gets overshadowed by louder ships. It's not flashy or overtly romantic in the source material, but that's what makes the fanworks exploring it so interesting. Writers have to build on subtext, on quiet moments of understanding, on the fact that they literally changed each other's entire worlds. You see a lot of AUs that explore what happens if one of them never got their powers, or if they met under different circumstances, and those often highlight how essential their partnership is, romantic or not.
That said, I've noticed a real shift in how their relationship is portrayed over the years in fandom. Early on, it was very dominant, but as the manga progressed and Orihime's feelings became more central, IchiRuki fanfiction often became more introspective, angsty, or fix-it oriented. There's a whole subgenre of post-war fics that deal with the fallout of their separation and the new dynamics, which can be heartbreaking but also deeply satisfying if you're into that kind of emotional weight. It's less about will-they-won't-they and more about how they navigate a profound bond that now exists alongside other commitments.
I also find the contrast between how they interact versus Ichigo and Orihime fascinating. With Rukia, it's bickering and pushing each other to be better, a real equals dynamic. That creates a different kind of narrative tension in stories—it's about clashing wills and deep understanding, not unrequited pining. That's probably why you get a lot of slow-burn, rivals-to-lovers, or established relationship fics for them, focusing on the partnership aspect. It feels very mature, in a way.