A.

Sixteen-year-old Mitsu Chikusa attends an industrial high school as an architecture student—or, at least, that is what she has been told by others. When she fell headfirst down a flight of stairs, the resulting injury gave her amnesia, leaving her unable to recall much of her past. After being discharged from the hospital, she returns to school, where she is greeted by her friends and Hideto Hongou—her boyfriend. Although there are a lot of gaps in her memories, Mitsu is relieved to know that s...