After the last great white shark in the world was killed by humans, it turned into a monster and began slaughtering them, ushering in the Age of Great Monsters. Heroes rose up everywhere, with sharks at the forefront. Then, one day, the great white shark suddenly disappeared. Everyone thought it was dead, but... it, or rather she, had simply been reborn in a body with even greater potential: that of a girl named Wakaba Mutsumi. She became one of the girl's personalities, waiting to bring terror to the world...
Nagasaki Soyo believed she would be trapped forever in that day: the day Mutsumi was eaten by a shark while saving her. The last time she spoke to Mutsumi, she had complained that Mutsumi wouldn't tell her anything about Sakiko. All she could do was cry and repent alone under her covers every night... until Wakaba Mutsumi, now with three heads, appeared before her again.
Progression: Great White Shark - Two-Headed Shark - Three-Headed Shark - Frilled Shark - Goblin Shark - Sharknado
Three personalities:
[Self]: Mutsumi
[Protection]: Mortis
[Release]: Same (Great White Shark personality)
The more their personalities meld, the more heads they grow and the stronger they become.
(If you enjoy bizarre stories, redemption stories, yuri, lifelong regrets, madhouse theaters, and gladiatorial combat, come on in.)