Under the command of the newly appointed Captain Masaki Yoshimoto, "Kawachi" was assigned to the Second Squadron of the First Fleet on 1 December 1917 and became the flagship of Rear Admiral . She briefly cruised off the coast of China in February–March 1918. In May the ship exchanged two of her three-inch casemate guns for three-inch anti-aircraft guns. On the evening of 11 July, "Kawachi" entered Tokuyama Bay, the following morning torpedo target practice was cancelled due to rough seas and the battleship remained at anchor for the rest of the day. That afternoon a loud explosion was heard at 15:51 in the vicinity of the starboard forward main-gun turret and large quantities of smoke erupted from the turret and between the first and second funnels. Two minutes later, she began to list to starboard and capsized at 15:55, only four minutes after the explosion. Over a thousand men were aboard "Kawachi" at the time of the explosion and over 600 were killed, with 433 survivors.