Looking for an old Ranma fanfic where he uses Hidden Weapons to walk through walls
I know this is a hell of a long shot and Ranma is an ancient fandom but hey, I still gotta try.
Anyway he learns Hidden Weapons from Mousse and figures out how to use the spatial distortion to do more than store stuff. He figures out how to phase through wall, it's ki-expensive but he can do it. I vaguely remember a scene where the narrator describes his thought process as contrasting between what a scientist who actually knows the topology and physics involved versus Ramna doing hulk speak.
I vaguely remember some kind of infiltration scene where he enters a skyscraper using said technique and he senses several strong ki signatures among the staff (it's possible Nabiki was kidnapped? I don't recall, the fic is definitely 2009 or earlier)