Chapter 5 is told from Shūya’s perspective, written as a “Last Will and Testament” on his website. Shūya admits that he “understand[s] why murder is considered a crime. But [he] do[es]n’t necessarily understand why it’s evil per se” (178). His birth mother is an electrical engineering genius who met his father (who runs an electronics store) during a hospital visit. Although they were initially happy, Shūya’s mother eventually regretted giving up her career to care for her child. Instead of telling him scientific laws as bedtime stories as she once did, she began physically abusing him. Once his father found out, Shūya’s parents divorced; his father got custody, and his mother left for a new job at a university. Shūya’s father remarried, and Shūya was happy until his half-sibling was born and his father’s new family abandoned him, giving him an unused property that became his laboratory. He seeks to regain his birth mother’s attention through his inventions, which are unappreciated by the students and family around him.

Shūya is initially drawn to Moriguchi, but he rejects her when she cautions him about his shocking coin purse. He convinces her to reluctantly sponsor him for a science fair, which he hopes will catch his mother’s attention.