One day during Yōta Narukami's last summer vacation of high school, a girl named Hina suddenly appears and proclaims herself "the All-Knowing God." Hina announces to the thoroughly confused Yōta, "The world will end in 30 days." Yōta then witnesses Hina's god-like powers of prophecy, convincing him that her powers are real. Hina's naive innocence belies her powers, and she decides to live at Yōta's home for some reason. Thus begins an eventful summer before the end of the world.
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