Okay, RPG recommendation time with twist in that I kinda already have something in mind but wish I could find something better: for years I've been longing to run a game that's an homage to Ranma 1/2's absurd approach to martial arts using Legends of the Wulin but outside of what I think is a fantastic combat system it's a hot mess. I've had FATE recommended to me but I really do want something that'd have more crunch to the combat, and 4E won't work because it's strictly co-op. Thoughts?
There are a few different ways you can go with this.
The first is Anima Prime, which does an excellent job of emulating not only the descriptive action, but the pacing of shounen fight anime, with dice flying around between different pools providing an actual mechanical reason you don’t just open the battle with your most expensive technique. It’s definitely more on the Final Fantasy XIII or RWBY end of the spectrum than the Ranma end, though, and tactical positioning is almost entirely a matter of abstract resource management; if you were looking for something that lets you get a concrete mental picture of the battlefield’s layout, Anima Prime is maybe not the best choice.
For something with slightly more concrete mechanics, you could also give Feng Shui 2nd Edition a spin. It’s a pretty solid system, but the issue you’re gong to run into here is that it’s pretty specifically aimed at 1980s live-action martial arts movies, and it’s big on systematising genre tropes - you’ll have a fair bit of work cut out for you scrubbing the serial numbers off. Also, in spite of its… enthusiastic tone, your average player character is actually kind of low powered for doing something like Ranma ½, much less anything on the really high end as far as shounen fight anime goes.
Finally, it’s a slightly oddball suggestion, but if you really want to go hard on combat crunch, have you considered a superhero system? Superhero comics aren’t exactly like shounen fight manga, but there are enough similarities that if it’s just the fighty mechanics you’re concerned with and you don’t mind winging the scene framing, the combat systems should be largely compatible. Going full HERO System is probably overkill for your purposes, but something like Wild Talents 2nd Edition could suit nicely. The Cortex-based Marvel Heroic Roleplaying would also be an excellent fit for Ranma ½, I think, though it’s out of print due to licensing issues, so good luck getting your hands on a copy.