I am an American living in Tokyo and I went to both concerts this past weekend. The vast majority of the Japanese who attended do understand a lot of English. They might not be able to speak well and they don't understand most of the slang phrases or play on words that JBJ uses, but they do understand enough of the lyrics to catch the general meaning of the songs. During the second concert JBJ asked the crowd for a show of hands of who also went to the first concert and about 15-20% of the crowd raised their hands. He asked a few other questions throughout the night and each time the crowd gave an appropriate response. Generally the chorus lines to Bon Jovi songs are fairly simplistic, catchy and clearly enunciated by JBJ. I think this is one reason Japanese love Bon Jovi. When Bon Jovi songs are played on the radio or are karaoked it is always in English. Nothing at the concert was translated into Japanese.