Diffuse dwarf galaxies are hard to find, but understanding the environments where they live, their numbers, their star formation, and ultimately their origins, is of intense importance for galaxy formation and evolution. Leveraging the deep and wide Hyper Suprime-Cam (HSC) Strategic Survey images, we search for ultra-puffy galaxies, defined as being 1.5-sigma larger than the average size for their mass, around Milky-Way--like galaxies in the local Universe. I will present a statistical study of their abundance, size, spatial distribution, and star formation properties. We argue that the ultra-puffy galaxy is more physically motivated than the well-studied ultra-diffuse galaxy. Surprisingly, despite being outliers in size, the ultra-puffy galaxies have a similar quenched fraction as normal-sized satellites of Milky Way analogs, suggesting that quenching is not tied to being a mass-size outlier. I will also discuss how will the upcoming surveys (Merian, LSST, Roman, and CSST) advance our knowledge of dwarf galaxies and dark matter.