When Yūta joins Rikka on her summer vacation, Yūta learns that two years prior, Rikka's father, to whom she was very close, died unexpectedly due to a terminal illness, causing her to fall into her delusions.
Ketika Yūta ikut dalam liburan musim panas, Yūta mengetahui bahwa dua tahun sebelumnya, ayah Rikka, meninggal mendadak karena penyakit mematikan, menyebabkan Rikka jatuh ke dalam delusi nya.