Official or high-quality fan translations often focus on the following to enhance the viewing experience:
The title itself is a metaphor: "becoming an adult" isn't about age, but about the moment innocence is lost and replaced by experience.
"Shounen ga Otona ni Natta Natsu" is a Japanese manga and anime series that revolves around a young boy who experiences a mysterious and transformative event during a summer, causing him to physically and mentally mature into a adult.
Cap 3 is the culmination of the tension built in the first two parts. The boundary has been crossed. Here, the story deals with the consequences—not in a negative sense, but in a revelatory one. The protagonist realizes he cannot go back to the boy he was in Cap 1.