She's a woman who admired the world-famous programmer Arata Mizunashi, known among gamers globally, and joined Iris Corporation—his former workplace—because of that admiration. Before Arata Mizunashi disappeared, he trained her for a brief time, and Mai herself is a brilliant programmer who could rival him. She's now an essential member of the End to Odyssey development team.

She holds herself and others to strict standards, which often leads to conflict with other staff members! However, most of the team understands her, so those clashes rarely escalate into anything serious. ...Except when it comes to a staff member named Akagi, and Mai's own father.

Mai finds her mental strength from phone calls with her younger sister, Sanae Toyama. She lives alone in an apartment near the company building, and since she doesn't get to see Sanae often, she's always eager to talk to her. Still, even while enjoying her happy conversations with Sanae, she can't seem to forget about her missing best friend, Rottie... She's quite eccentric, but she slowly grows close with Sayaka, who joined the team as a part-timer. Surprising, isn't it? In truth, an unimaginable parasite stirs inside her body—something with the power to decide the fate of many. She's been trying to keep it suppressed, but... will she be able to keep it under control when the threat to the world draws near?