This reminds me of how in every Platinum Games title you have a rival character with the same moveset as you and you guys are enemies first but by the end of the third act a greater enemy comes up and you both team up to fight it.
Also, to the translator - interesting note on the ninja names. Honestly, either version still works, since the joke is that they have redundant names. The former is more jokey, while the latter is more serious - but since this IS One Punch Man, they both fit different situations.