Zennou no Noa - World of Lostmemories
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2038年、東京都心で突如発生した『100万人同時記憶喪失』。大量に発生した発症者を保護するため、政府は東京の地下に隔離施設『東京地下都市（ジオフロント）』を建設した。しかし、そこは『記憶を持つ者（アダルト）』が『記憶を失った者（キッズ）』を支配する、偽りの楽園だった──。 [Official Site]
In the year 2038, a white light descended on the center of Tokyo and stole the memories of over one million people. The cause of this horrible incident was not determined, and no cure was to be found. The government formed a separate city beneath Tokyo to house and care for the victims of the incident and branded them as "KIDz." Regardless of their age, they truly are like children, and they must be retaught everything they once knew. Noa Ikurumi, who lives in this isolated society, is just taking one day at a time and dreaming of finally being allowed to go back out into the world. But Noa's life will once again change drastically on the day that he is taken hostage by a terrorist with some surprising information about his identity...