Shinto was the main religion practised in Japan at the time. It was native to the country and a confirmed date cannot be shown as to when it was introduced to the Japanese.
Buddhism was the second major religion in Japan. It was approximately introduced in the 6th century and has been a part of Japan ever since.
Christianity is a relitivaly new religion in Japan, first being introduced by Francis Xavier in 1549. Many Christians were persecuted and killed, then it was later banned in around 1626.