Rio Sanada is the president of "Sanada Wellness" and an up-and-coming businesswoman who is selected as one of the "100 people in their 30s who will change the world". She is reunited with her former love interest Daiki Miyazaki, who is now a detective, after 15 years as an important witness to a murder case.

In Gifu Prefecture in 2006, Rio is a third-year high-school student who wants to go to the University of Tokyo. She took good care of her younger brother in lieu of their busy father. Before Daiki could confess to her, an incident occurs at the dormitory.