Yuu's older brother, Shuu, crosses paths with Koizumi one morning; after learning about hiyashi ramen from Koizumi, the girls are enticed to try it on a hot summer day; Koizumi encounters a lost little girl while she visits a museum.
Yuu tries to invite Koizumi to a hamburger restaurant; Yuu joins Koizumi at a ramen restaurant where the seats are flavor concentration booths; After finding Koizumi collapsed from starvation, Yuu brings Koizumi to her house.
Yuu follows Koizumi after school believing she is meeting with a boy; Yuu and Misa visit a ramen restaurant after a day of shopping; after having a stressful day, Jun goes to a convenience store and ends up eating ramen there with Koizumi.
Yuu provides commentary as Koizumi enjoys a bowl of tomato ramen; Jun goes with Koizumi to try a green ramen that is rich in euglena; Yuu waits in line for a popular ramen shop in place of Koizumi after learning she dislikes long lines.
While Yuu and Misa go to the beach, Koizumi and Jun go to a shop that sells a variety of instant ramen from all across the country; Shuu and his friends go to a ramen shop that serves iekei-style ramen.
Summer break has started and Yuu, Misa, and Jun go to an amusement park and visit the city of Asakusa. While in the city, Yuu comes across Koizumi on a "nationwide" ramen tour.
Koizumi goes on a mountain hike; Misa's younger brother, Kenta, becomes motivated to finish the massive Buta Yarou ramen when he sees Koizumi; Misa follows Koizumi to a ramen shop that sells ramen full of pork back fat.
Yuu tries to recall the name of a ramen she had when she was a little kid; Koizumi travels to Osaka to try the ramen there and is accompanied by a woman who decides to act as her bodyguard.
Yuu witnesses Koizumi eat ramen that has a blue broth; Shuu takes Yuu to sushi bar where Koizumi also happens to be at; the four girls go to a Chinese restaurant.
After her boyfriend breaks up with her, Misa follows Koizumi to a ramen shop where they both order the spicy Hokkyoku ramen; Jun finds herself visiting a ramen shop after learning about peculiar ramen flavors from Koizumi.