Wow nice find! I don't know but everything on this sounds like Purity Ring if you ask me, first this is definitely Megan's voice, and the music arrangement screams Corin too lol. also the title "Bitter Rhymes" was listed on this song register site since a long time.
And even if it's not, I wanna hear the full one because it sounds fantastic!
Edit: Shazam said it's Purity Ring too! and they are mostly right.
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£13.80 on amazon, thank me later!