Wish I could be more helpful, but on the bright side simply the fact that you have an actual street name in the address indicates it as a major one (most Japanese addresses are nothing more than divisions of subsections of districts within wards (Chomes), blocks and then houses or building #'s. In this case it would likely translate to 3-2-0 Mifune. the first being Chome 3, Block number 2 and building 0 (?). Streets are also numbered in the order they were constructed, not sequentially, so with so much reconstruction after the quake, many addresses may have changed as well.....Surely there are name & address finders out there somewhere that could at least see if this one ever did exist, however.