Although Christian churches have been preaching in Japan for 500 years, Christians make up only 1% of the population.
Moreover, Japanese Christians also go to Shinto shrines to pray.

There are a lot of Shinto shrines and Buddhist temples all over Japan, and Japanese people like to pray there. However, many of them say themselves as non-religious.
I was puzzled by this for a long time, but recently I've come to understand it. Japanese people believe in God, but they don't rely on religion.
That's why even Japanese Christians pray at Shinto shrines.