Miku was just a regular high school girl who loves nails. But suddenly, she got into a terrible accident and the shinigami (death god) Sei fastened Thanato's Lover, his chain of death, onto her wrist! However, she was taken by mistake and was brought back to life but the chain cannot be removed until the end of her lifespan.
Miku loves doing nails and she seems to be really good at it since her school mate does ask her for help. She even asked to do Sei's nails once and he reluctantly agreed to having one nail done. Even when she went to visit Jun, she made sure to bring her nail basket along.