One-Punch Man

[Buffalobiian]

What shinta says makes complete sense though.

[Kraco]

What shinta says makes complete sense though.

I don't still understand it. They are Japanese words, so they should be written in hiragana if they aren't written in kanji (or if it's a chuuni kanji that nobody knows how to pronounce). However, if it's something fancy like a hero name, it would make sense they could use katakana since it's apparently used to mimic the Western italic effect, special effects, robot voice, and such things. So, to make it mark an artificial name, like a hero name, would be highly natural.

I guess I just can't understand it because I haven't much studied the Japanese language.

In any case, both sisters take their hero business far too seriously, so it wouldn't surprise me if once upon the time, when they were born, they were given regular Japanese names, but later they changed their actual names in the government citizen register into their hero names. So, Fubuki and Tatsumaki would be both their real names and their hero names.