It ties into the Oden narrative and was a hint towards Zoro cutting Kaido plus a tangible way to develop Zoro's haki. I never denied its a powerup lol. You're the retard who's counting it twice.
Yeah twice training and sword itself.
You can't do basic calculation
Dude it's literally just like Gomu Gomu no Fuusen, its a fucking move. Pre TS Fuusen was able to negate hits from fucking Sengoku. But its very situational, just like foxfire style. If the situation is right it's overpowered. Else its nothing more than a party trick.
Both Fuusen and foxfire style aren't powerups lmfao.
Fuusen was used way before MF to help the Merry reach GrandLine.
Fuusen didn't negate shit. Luffy is already immune to blunt attacks. Fuusen allows him to increase his surface so he could save Mr3 who was on the platform.
Luffy didn't learn fuusen from someone.
Explain why Zoro tried to learn it from Kinemon if it's not an actual PU ? It's like saying Rasengan isn't a PU for Naruto.
You don't even know what is a PU.