Asahi Kuromine, a high-school boy who has trouble keeping a secret from anyone, has a crush on his cool and reserved classmate Yōko Shiragami.

Asahi tells his friends that he decided to be just friends with Yōko for now. Meanwhile, Nagisa reflects on how she brutally rejected Asahi the previous summer to prevent him from getting too close to her, but now acts jealous after seeing him with Yōko.

Mikan tortures Asahi and his friends for more information about Asahi's meeting in the classroom with Yōko, but he refuses to tell her anything, fearing that she would spread the information around school like she did in the past.

Nagisa begs Asahi for help as her External Unit ran out of battery power before it could recharge and she was forced to come to him in her lilliputian form.

After discovering that UV rays from sunlight cause Yōko's skin to instantly tan, Nagisa decides to train her into dodging sunlight on her route to and from school.

After being relentlessly teased by Shiho's body in school, Asahi begins to projectile-nosebleed while Nagisa starts to get jealous.

Asahi finds out he has to retake a cooking class, having missed the previous one. He is delighted to find out that Yōko, Nagisa, and Shiho are joining him in making curry, but soon finds out that all three girls have trouble making it.

Now that it's summer, Asahi gets up the nerve to invite Yoko to the pool. The problem is, Yoko doesn't know how to swim and thinks that Asahi is asking her so they both could practice.

Okada, Sakurada and Shimada invite Asahi and Yoko to join them at a buffet restaurant, but Yoko is reluctant for fear of revealing her secret.

Asahi and Nagisa were invited by Youko, Shimada, Oka, and Sakura (respectively) to the Summer Festival; however, Youko tricked them into together on them spending an exciting time 'alone together'.

After the incident at the Summer Festival, Youko has been avoiding Asahi, unaware of how she really felt about the incident.

Asahi, Akari, Nagisa, Shiho and Akane pursue Youko, but are hampered by Akari's refusal to exceed the speed limit and risk damaging her new car.