The black envelop is a special invitation given to a chosen few who have earned the right to be in a special Survival Game tournament, those given to the members of Team Toy Gun Gun and to a certain man dressed in a white lab coat, who works as a pediatrician. On Masamune's call, Yukimura goes on to help Hotaru buy her own Survival Game gun, as a commemoration of her joining the team after a small pep talk from her seniors, only to be left to go shopping alone to the store. Lost and confused, she meets a seemingly kind stranger who seemed knowledgeable enough in regards to survival games and guns, who advises her on buying a gun, but what are his true intentions?