The story and characters cannot be properly rated, as this is a one shot, but it's suffice to say that the characters are simple and straightforward. The likewise simple story presented in Kanojo to Natsu to Boku could have developed into a manga with great potential if it was continued.
The art is in full color, and the excellent color contrasts ups the visual quality of the one shot greatly.
Overall, Kanojo to Natsu to Boku features an incredibly short but enjoyable scene. It only took me about a minute to read it, but it was worth the minute.
