Gamma rays are produced when the cosmic rays interact with matter, magnetic fields or light in or around the sources or in interstellar space, and travel across the Universe to galaxies beyond, transporting with them the secrets of their birthplace. The University of Tokyo participates in the ground-based Cherenkov Telescope Array (CTA) which detects cherenkov light of air shower produced by gamma rays in the atmosphere of the earth. CTA Japan group consists of 29 universities and institutions has been contributed to construction and management of the Large-sized Telescope (LST) at CTA north site in Canary Island, Spain, to study very high energy gamma-ray astrophysics.