Kokoro

Kokoro, こころ is a 1914 Japanese novel by Sōseki Natsume, and the final part of a trilogy starting with To the Spring Equinox and Beyond and followed by The Wayfarer (both 1912). Set in the Meiji era, the novel tells of the acquaintance between a young man and an older man called "Sensei" ("teacher" or "master"), who holds a secret from his past regarding the death of a friend.
Kokoro was first published in serial form in the newspaper Asahi Shimbun. Along with Osamu Dazai's 1948 No Longer Human, Kokoro is one of the best-selling novels of all time in Japan.