Answer it yourself gez last people
The Japanese adopted forms that met with their needs.
There is no "regular" Buddhism. There are a number of schools of Buddhism. Zen is one school that originates from Japan.
This depends of the form of Buddhism you're talking about. Early Buddhism came from India, and so has strong Hindu roots. Mahayana Buddhism was most popular in China, and has very strong Taoist elements. regional forms of Buddhism - particularly Tibetan Buddhism and Japanese Zen - are often influenced by local religious traditions.
Zen Buddhism and Shingon Buddhism are two notable sects of Japanese Buddhism. Pure Land, or Amidist, Buddhism is also significant in this country. Pure Land has its roots in India and China, however. Zen Buddhism emphasizes meditating for enlightenment. Shingon Buddhism is a type of Pure Land Buddhism and is esoteric and relies on early Buddhist Tantras.
Katanas (Japanese Longswords), anime, manga, haikus, Japanese music, karate, animation styles, art styles, various forms of sushi, and the Japanese language.
I am particularly interested in Japanese culture. The rich history, unique art forms such as Ikebana and Kabuki, the traditional tea ceremony, and the aesthetic principles of Zen Buddhism all captivate me. I find the emphasis on harmony, discipline, and attention to detail fascinating, as it is reflected in various aspects of Japanese life, from their architecture and cuisine to their traditional arts and crafts.
The official introduction, according to the Japanese records actually happens in 552 CE when monks from Korea, this time, came to Japan and introduced the principals precepts of Buddhism and brought some treasures with them. The first years were not actually easy as Buddhism became one more tool in the struggle for power over the imperial dynasty by the Soga clan over the rival Mononobe and Nakatoni clans. more info at the related link.
The Chinese adopted it and created other forms of it such as Zen and Pure Land Buddhism
'eku' used to be a Japanese weapon, a bit like an oar 'écu' was, in various forms, a French coin
It depends which country you are referring to.Governments have different working principles. In some countries the principles are set out in a constitution, others through common laws of precedence. Some countries have various forms of absolutism where the principles may change according to who or what is the ruling power.
I assume you mean the religion of the Japanese? If that's the case, the answer would be Shinto as well as Buddhism. There is not one religion for the entirety of the Far East. In general broad strokes, there is Shintoism in Japan, Buddhism (in various forms but mostly Mahayana and Zen) across East Asia, Juche in North Korea, Christianity (primarily Protestantism, but also some Catholics) in South Korea and Japan, along with Daoism and Confucianism in China.
There were two major forms Buddhism took as it spread out of India: Theravada and Mahayana. The Mahayana further subdivided into a number of smaller schools.