TOKYO — For over 40 years, Japan’s leading purveyor of shadowy phenomena, Mu magazine, has peddled Bigfoot, U.F.O.s and the occult to a ravenous fan base. Alien civilizations and the biology of the Loch Ness Monster have been popular cover stories. A conspiracy theory doesn’t quite arrive in the country without a nod from the monthly publication. Yet Mu, with almost 60,000 readers and devotees inc