サマーウォーズ (Series) favorite_border

[DeepL Translation - needs review] Kenji Koiso is asked by Natsuki, his senior whom he admires, to "pretend to be my fiancée for four days! and he decides to accompany her to the countryside in Nagano Prefecture. That night, Kenji receives a mysterious sequence of numbers, which he solves, and his world changes forever!　Sneaker paperback edition with lots of illustrations!

(Translator: DeepL)