My research interests are neutrino particle physics, neutrino astronomy, the search for the character of dark matter, and the experimental verification of the Grand Unified Theory (GUT). The observation of atmospheric, solar and accelerator neutrinos at Super-Kamiokande (SK) demonstrated that neutrinos have masses and change their species while traveling in space. I will perform a precise measurement of solar neutrinos, and investigate neutrino masses and mixings. If a supernova happens to appear in our galaxy, SK is able to detect about 10,000 neutrino events, and it would reveal the detailed mechanism of the supernova explosion. And if the supernova neutrinos accumulated from the beginning of the universe (called supernova relic neutrinos) are observed, they should tell us about the history of star formation in the universe. It is well known that dark matter accounts for 20% of the energy of the universe, but the character of dark matter is not known yet. I want to unravel its character by a low background underground experiment. I would also like to find experimental evidence of GUT through proton decay.