That made me realize

You used yourself as the sacrifice for your own whistle

A story about a timeline in which Riko and Bondrewd's positions are exactly opposite of the original manga

Wow!

Spot on!!

Just what I'd expect from Bondrewd-san!!

But your mask is still creepy though.

And perhaps the experiments with those "cartridges"

were a byproduct of attempting to find a method to create more "life-reverberating stones," were they not?

Ooh!