In a small Tokyo apartment, twelve-year-old Akira must care for his younger siblings after their mother leaves them and shows no sign of returning.

The purportedly true story of a 23-year-old otaku (Japanese geek) who intervened when a drunk man was harassing a woman on a train. The otaku ultimately started dating with her and chronicled his event and his dates with the woman (who became known as "Hermès") on the Japanese mega-BBS 2channel.

Kae Horii moves into her new flat in an undisclosed area of Kyoto. While unpacking her belongings, she discovers a hidden compartment behind a inconspicuous mirror. In that compartment, Kae finds a notebook, that turns out to be a diary belonging to the previous tenant. Later that evening Kae starts to read the diary. The writer of the diary is Ibuki Mano, a young lady about to embark on her first year as an elementary school teacher. Ibuki is also in love with a man named Takashi, who may or may not hold similar feelings for Ibuki.

What's scary is being a human being, and what's scary is being myself. Truly horrifying things reside inside oneself. The work asks if you can stand the inescapable terror.

The making of the movie "Nobody Knows" by award-winning director Hirokazu Kore-eda.