[quote=@Moonlit Sonata]
<Snipped quote by Kost Alter>

The Monte Cristo Mythologie method would make it fine. It's just a matter of reconciling the monstrous transformation with the magecraft usage, which that does, since it petitions the effects cleaner. 
[/quote]

Hmmmm, I see... How about adding the following:

[hider=click me]
By having implanted the Tide-Controlling Jewel into her body, not only has Tamatori mutated into a half-human, half-octopus sea monster with superior strength and swimming ability, but she has also gained access to new magical powers, heralding her newfound status as a "successor of the Sea God". Acting in a way similar to a Magic Crest, the pearl has carved special Magic Circuits into her body that she didn't previously possess, which makes her capable of practicing Water Element magecraft of the highest level. She can manipulate water to her will, use water as a form of attack, or generate streams of water to crush a single enemy. However, such magics are merely an artificial reenactment of the true power the Tide-Controlling Jewel grants its holder as one with absolute control over the tides and the sea itself.
[/hider]

That would be acceptable, right?