Not a Seabird

Prompt 2: Flight! You don’t know this person! Why are they calling you Ronin?! Get away! Draw or write your character swimming for their life from the mermaid who lured them here.

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What a predicament indeed.  First Bertrand finds himself submerged in a deep body of water with no recollection of how he got there, now he's being accosted by a disgruntled mermaid.  The first thing he noticed was despite being under water, he could hear her perfectly.  Secondly, he was certain that is was her voice he heard in that eerie song before he blacked out.  Thirdly, she kept throwing around the name Ronin.  He knew who that was - he's seen to the apothocary before, and even looked after his shop on occasion.  What did Ronin do to make this woman so upset?