Reprinted dozens of times since it was first published in 1967, "The Legal Consciousness of the Japanese People" by the late Takeyoshi Kawashima is arguably the most influential book on Japanese law ever written.
One of Kawashima's theories is that traditional Japanese society lacked a strong consciousness of rights. After the Meiji Restoration of 1868, when the government started translating Western legal codes to use for Japanese laws, there wasn't even a Japanese term that could be used to express the concept of a "right," so a new one had to be invented. With this cultural foundation, notwithstanding the introduction of Western-style courts and legal codes, the notion of using the former to assert rights under the latter never really took root.
Non-litigiousness remains an integral part of the "Japan is different" canon that Japanese people recount to foreigners and each other. While Kawashima's explanation has been influential and merits attention, it is due some skepticism as well. I consider it noteworthy that just a few years after the Meiji Restoration, the new government created a statute of limitations. This suggests that whether or not the average Japanese person thought about asserting their rights, from a very early stage the nation's leaders saw a need to restrict their ability to do so.