The story might revolve around a young protagonist who undergoes significant life changes during the summer. This could involve personal struggles, new relationships, or pivotal moments that lead to the protagonist becoming more mature or "an adult." The summer setting could symbolize a period of freedom, exploration, and self-discovery.

Without more specific information about the episode, including its actual title, the series it belongs to, and a detailed plot summary, this report remains speculative. However, it's clear that "the summer when the boy became an adult" hints at a poignant and potentially transformative episode in a larger narrative about growth, maturity, and the journey into adulthood.

The episode in question seems to focus on themes of growth, maturity, and possibly nostalgia, given the title's implication of a coming-of-age story set in the summer. Without specific details about the plot or the series it belongs to, we can only speculate on the content.