Hachiman is trying to relax during summer break, but is eventually tricked by Komachi and Shizuka Hiratsuka, along with Yukino, Yui, Saika, Hayato, Yumiko, Kakeru and Hina to help out at an elementary school's summer camp at the Chiba Mura Park. When they finally arrive Shizuka explains to Hachiman that it will provide a good opportunity for him and Yukino to interact with people from other social cliques.
As the activities begin, Hachiman and Yukino immediately notice Rumi Tsurumi, an elementary school loner, being shunned by her classmates. Hachiman and Yukino observe Hayato's failed attempts to talk to Rumi, which prompts her to walk away towards Hachiman and Yukino. Rumi explains to them how her situation came about, and resolves to make friends in middle school. Yukino explains the flaws in her plan, as Rumi will probably end up in the same middle school as those ignoring her now, and their behavior will likely be adopted by the new students as well.
During dinner that night the Sōbu High School group discuss Rumi's circumstances and try to come up with ways to help her. Later, Hachiman, unable to sleep, goes for a walk and finds Yukino out stargazing. Yukino explains that she inadvertently made Yumiko cry after spending thirty minutes arguing with her. Yukino also tells Hachiman that she wants to help Rumi because she reminds her of Yui and that Hayato's inability to do anything for her may be bothering him. As Hachiman asks about Hayato, she explains that she knew him since elementary school and that his father is an adviser to her family's company, finally saying that she's glad she was able to come to the park and leaves for bed.
Hachiman, now alone, looks at the stars. Rumi is shown sitting alone by the riverbank.
While Yukinoshita Yukino is staring at the loner girl and sighs, Hikigaya Hachiman comments about how "Stand Tsukai attract other Stand Tsukai..." It is clearly a reference to the anime "JoJo no Kimyou na Bouken