The idea of being Japanese takes precedence over everything else in Japan. According to Wiki over 50% of the Japanese follow Shintoism (worshiping ancestors, nature) and around 40% follow Buddhism. In the practical Japanese world however, it is very normal for a person born into Shinto faith to have a Christian wedding and on his death, a Buddhist funeral. The idea of being Japanese is so intertwined with Buddhism and Shintoism that most religious practices may well be considered traditional Japanese customs and rituals.
There is no serious “religious education” in Japanese schools. So from childhood there exists a kind of indifference towards religious differences.