Aki Masuzu is from Ehime Prefecture, like prefecture as Iyojima Anzu and Doi Tamako. During the initial Vertex Invasion, she guided them with her Miko abilities in using their Hero powers to protect the evacuating citizens.
She is in constant contact with the Shinju but often complains about her duties (such as bathing in the waterfall to purify herself).
Masuzu is a pale-skinned teenager. Her hair is in a braid in the shade of khaki. Her eyes seem to be a dark brown and as Miko, she wears her red dress and white haori.
It seems she likes to complain about her duties most of the time. Though it seems she cares greatly about the people around her as well.
As a miko, she is able to see vertex attacks, their numbers, and guide the heroes to sacred weapons before weapons were added to the terminal.
Masuzu guided Anzu and Tamako to their weapons in the initial vertex attacks and since have become friends since then. She came back again during their funeral and was regretting not hanging out with them more often.
She seems to care greatly for Tamako, she led her to her weapon back in the early vertex attacks. When she attended her funeral she was sobbing her eyes out for her and Anzu.
She seems to also care for Anzu as she has also guided her to her weapon and bawled her eyes out at their funeral together.