First-year Takatoki Nanami has only one chance left to redeem himself from his poor academic performance. If he fails his supplementary exam, moving on to the next grade will be impossible. A ray of hope shines on him when he makes an awkward first impression on Kei Takanashi—a third-year student who excels at his studies yet appears cold and distant. Blackmailed by Nanami, Takanashi reluctantly agrees to become his tutor.

Nanami's perseverance quickly makes up for his lack of intelligence, and his review sessions with Takanashi slowly break the ice in their relationship. Soon enough, Nanami passes all of the tests; but despite their agreement being fulfilled, Nanami is not yet ready to let go, wishing to learn more about his senior.

Hidamari no Orange has been licensed in English as Sunny Orange by Gush Comics.