Also known as: 虹森未央子, デガスちゃん
MIO5 is a character from Ojisan To Marshmallow.
Her name is pronounced Mioko. "Ko" is one of the pronunciations for 5.
Her nickname is Degasu-chan (デガスちゃん), because of her tendency to end sentences with "degasu".
Her full name is Koumori Mioko (虹森 未央子).
She is an illustrator at the same company as Hige Habahiro and Wakabayashi Iori.