KAGRA, the underground and cryogenic laser interferometer for gravitational wave detection

The gravitational-wave detector, KAGRA, is unique for its underground site and cryogenic design. The first observation started from 25
^th
February 2020 with a limited sensitivity of 400 kpc for binary neutron star inspirals for two weeks. From 10
^th
to 24
^th
March 2020, the observation is in a brake for further detector commissioning to attain 1 Mpc sensitivity to join LIGO-VIRGO observation network. This paper reviews the commissioning efforts including the lock acquisition procedure of the KAGRA interferometer.