We report initial results of the studies probing star forming galaxies with nebular emission at z<1.5 in wide fields of ~20 square degree based on the HSC-SSP narrowband (NB) data. The NB816 and NB921 data currently available allow us to select >15,000 Halpha emitters at z=0.2 and 0.4, >15,000 [OIII] emitters at z=0.6 and 0.8, and >35,000 [OII] emitters at z=1.2 and 1.5. Both of the depth and the survey area make the samples very unique to study evolution of typical star forming galaxies. We have found there are large-scale structures of star forming galaxies at z<1.5 and a dozen over-density regions embedded in them which are candidates of active galaxy clusters at z~1.5. In the conference, we will discuss the luminosity functions of the individual emission line galaxies. The wide-field data allow us to overcome the cosmic variance and thus to obtain the most reliable measurement of the luminosity functions. Then, we would like to discuss environmental dependence of the shape of luminosity function. We also report a discovery of >100 star-forming galaxies with a large equivalent width of nebular emission of >500A which are candidates of low-metal young galaxies, that is, a key population to understand galaxy formation and evolution.