The "bib" worn by the Japanese monk in the photograph is a rakusu, a garment unique to the Zen school that may have originated among Ch'an monks in China sometime after the T'ang Dynasty. The rectangle worn over the heart is a miniature kashaya, complete with the same "rice field" pattern seen in the third photo in this gallery. The rice field in a rakusu may have five, seven, or nine strips. Rakusu also come in a variety of colors.
Generally in Zen, the rakusu may be worn by all monks and priests, as well as laypeople who have received jukai ordination. But sometimes Zen monks who have received full ordination will wear a standard kashaya, called in Japanese the kesa, instead of the rakusu.
The monks' straw hat is worn to partly cover his face during the alms ritual, or takahatsu, so that he and those who give him alms do not see each others' faces. This represents the perfection of giving -- no giver, no receiver.
In this photo, you can see the monk's plain white kimono peaking out from under the black outer robe, called a koromo. The koromo is often black, but not always, and comes with different sleeve styles and diverse numbers of pleats in the front.