This is the second time that these Japanese had visited Shan

这句话是错的.“第几次做某事”的两种表达方法：
1、It/This/That is the first time that + 现在完成时；
2、It/This/That was the first time that + 过去完成时.
所以要么是：This is the second time that these Japanese have visited Shanghai.
要么是This was the second time that these Japanese had visited Shanghai.

你的怀疑是正确的，前面是is，后面应该是现在完成时。前面是was，后面应该是过去完成时。