Sasebo Naval District
"W-7" was laid down on 27 October 1937. On 16 June 1938, the ship was launched, and numbered "W-7". On 25 December, it was attached to the Sasebo Naval District. On 1 June 1941, it was assigned to MineSweepDiv 21 with "W-8", "W-9", W-10, "W-11" and "W-12".