She participated in the invasion of the Northern Philippines (Operation "M") in December 1941 where she was assigned to Sub Chaser Division 21 (SCD 21) led by Commodore Ota along with , , , , and . SCD 21 was at the time assigned to Rear Admiral Hirose Sueto's 2nd Base Force under Vice Admiral Ibō Takahashi's Third Fleet. She served mostly on escort duty during the war. On 26 August 1943, while escorting transport "Amagisan Maru" and fleet oiler "Tsurami", she was attacked off the coast of Palau by captained by Lieutenant Commander James A. Scott; Scott was forced to abandon his efforts after "CH-4" damaged his submarine with depth charges.