Hikari's mother begins to tell the truth that she had hidden to Futaba-chan, who came to hear about Sako. Previously, when Hikari's parents, Futaba's mother, and Liang Cho's father worked for the same pharmaceutical company, Hikari's father invented a drug that causes brain damage when taken in large amounts. It was being abused. Hikari's parents and Futaba's parents, who knew it, tried to stop selling the drug, but Liang Cho's father tried to hide what they said in order to protect himself.
