Megalo Imposter Rin - What's the deal?

[BlackUmbrellas]

So besides getting a free weapon... is there anything special about them?

[UmbreonMessiah]

The absurdly high base movespeed and might, on par with Red Death.

[GuineaPrince]

You can give him tongue a second time, and the arcana for counterparts, and just have him tongue the entirety of the screen to death.

[Rusty Knight]

if you take tongue 2nd time and max it out (not sure if evo is required), you end up with 6 or 7 tongues (as in, separate weapons), all but the one you've picked up manually are hidden, but you can see them in the post-game statistic