Hasegawa is a quiet and unassuming high school student who tends to blend into the background. His ordinary life takes an unexpected turn when Hiyama, a popular and sunny social butterfly in their class, suddenly confesses his feelings. The central conflict arises from their shared inexperience; neither boy has ever dated anyone before, and Hasegawa is shocked to discover that his popular peer is just as clueless about romance as he is.

Set in a contemporary Japanese high school, the story follows how two complete novices navigate the early stages of a relationship. Unsure how to interact with a classmate he has never spoken to, Hiyama proposes an old-fashioned solution: a diary exchange. This unconventional method becomes the core narrative device, as the two boys write down their thoughts and feelings, passing the notebook back and forth to communicate when words are too difficult to say aloud.

The main narrative arc focuses on the diary exchange as a bridge between their two different worlds. Through each entry, Hasegawa and Hiyama gradually overcome their awkwardness and begin to understand one another. The story explores their journey from being strangers to discovering a genuine emotional connection, entry by entry, as two romance novices find their way toward love.