Mei-chan's real name is Akari Uoza (魚座 明).
Akari is Hikaru's younger sister. She is a seraph just like Hikaru. Frequently mentioned in Hikaru's stories, she doesn't make an appearance until much later. Her nickname is Mei-chan, because Akari can also be pronounced as "Mei".
Although Akari seems obedient to her older brother, she actually thinks Hikaru as an "incompetent fool". Her rank among the Seraphim is unknown.
Akari throws javelins. Just like Hikaru, she is able to turn feathers on her wings into javelins. Her accuracy, however, is anything but something to boast about.
Akari's main body color is white. Her paw tips and her ear tips are pink. Her hair tuft is also pink. Her eyes are heterochromatic like Hikaru, but the colors are switched.