JAPANESE prose today falls into four groups, called by the Japanese jun bungei (pure literature), puro bungei (proletarian literature), taishu bungei (mass literature) and tsuzoku bungei (popular literature). Of these, is the name applied to the long stories of contemporary life that discuss social problems without any particular literary pretensions. They run serially in the newspapers and women's magazines. Much of their material derives directly from the daily news columns. Mass is the direct offspring of the kodan, the historical romance of the old story-tellers' halls. It is full of armor, castles, feudal vendettas and swords, especially swords. The colorful old kabuki drama on the legitimate stage and the sword-play school of talkies on the screen use the same material. The so-called masses (which means almost everybody) delight in it. Old spy and detective stories are naturally grouped with this class. It is modern Japan's literature of escape. Through it, tired moderns can go back for a time to the idealized romance of old Japan. It is the life-blood of several popular magazines. Proletarian is written by working people and their intellectual sympathizers and deals with factories, tenements, strikes, laborers, farmers, policemen and prisons. It has been largely an expose motivated by a definite Marxist purpose. Government suppression has all but killed its special magazines. Pure is all the rest. Just before it got its last name, it was the new literature, taking much of its material from the caf6s, dance halls and ultra-modern life of the young bobbed and waved class. It is strictly up-to-date, pseudo-scientific and sexy, and strives to be literary and psychological. Most of it comes out in the literary pages of national reviews, which still print some proletarian literature.