Blastoise: Now... Who the hell Are you...
(さて・・・てめえが一体何者で・・・)
Blastoise: I'll ask why you're impersonating Murasame all this time after this.
(何で今更ムラサメになりすましてきやがったのかはあとで聞くとして)
Blastoise: If you don't even know why what you're doing is so fucked up, I'll tell you why...
(もし何も知らずにやらかしてんならダサすぎるから教えておくぞ・・・)

Blastoise: Murasame... The Real Murasame, is long dead
(あいつは・・・本物のムラサメはとっくに死んだよ)
Blastoise: I saw it with my own eyes
(俺の目の前でな)

That makes sense.

But that's not exactly the kind of info that can be kept hidden from the world for a dramatic reveal like this. Pops and Murasame were famous enough that this random Vappy knew about the nicked mane, but not that the owner of said nicked mane was dead?

Maybe Murasame wished for an in-universe "extra life" as insurance against the Poisoner's slash, except that the second go-around didn't actually preserve who he was as a person... or even most of his memories...