© 2006-2015 Bob Hackett, Sander Kingsepp and Peter Cundall
24 May 1944:
Tokyo. Laid down at the Uraga Dock Co. Ltdís shipyard as Kaibokan No. 5251.
25 August 1944:5 September 1944:
23 October 1944:
Completed and registered in the Kure Naval District. Reserve LtCdr Mitsui Tsutsumi is the Commanding Officer. Attached to the Kure Guard Unit at Tsurumi for training and workup.
25 November 1944:
Reassigned to the General Escort Commandís First Surface Escort Division.
23 December 1944:
Escorts an unidentified convoy between Moji and Singapore.
6 January 1945:
At 0750 departs Amoy with kaibokan SHINNAN and destroyer ASAGAO escorting convoy TAA-01 consisting of nine unidentified merchant ships bound for Takao.
7 January 1945:
At 1223 SHINNAN arrives at Saei. The rest of the convoy presumably arrives at Takao soon after.
4 February 1945:
At 0800 YAKU departs Singapore for Moji with kaibokan CD-13 and CD-31 escorting convoy HI-88-D consisting of ENGEN, DAIGYO and HARUYASA MARUs. 
5 February 1945:
A surfaced enemy submarine is sighted at 04-55N, 103-40E. At 0830, the convoy changes course.
6 February 1945:
At 0230, YAKU's lookouts sight a surfaced submarine and the convoy successfully evades. At 2157, Cdr (later Rear Admiral) Frank W. Fenno's USS PAMPANITO (USS-383) fires six torpedoes and sinks gasoline-laden ENGEN MARU in a ball of flame at 06-31N, 106-12E. DAIGYO MARU drops a few depth charges while YAKU searches unsuccessfully for the submarine. CD-31 rescues survivors and returns to Singapore.
7 February 1945:
At 0300, YAKU detects USS PAMPANITO off the port side. The convoy turns away. At 0454, a second submarine, LtCdr Ralph H. Lockwood's USS GUAVINA (USS-362) fires six torpedoes at the convoy and sinks DAIGYO MARU in five minutes at 06-58N, 106-08E. USS GUAVINA surfaces and her crew takes pictures of the oil-clad survivors, many of whom fake death. At about 0800, YAKU finds and rescues the survivors of DAIGYO MARU.
8 February 1945:
The convoy makes port at Cape St. Jacques, Indochina where it is dissolved. At 1830 YAKU arrives at Saigon.
9 February 1945:
At 1000 YAKU departs Saigon.
13 February 1945:
At 1420 arrives at Singapore.
16 February 1945:
At 2100, YAKU departs Singapore with kaibokans CD-13 and subchaser CH-57 escorting convoy HI-88-H consisting of HONAN MARU, oilers EISHO and NICHIYOKU MARUs.
22 February 1945:
At 1045, NICHIYOKU MARU is torpedoed and sunk by LtCdr Henry D. Sturr's USS BECUNA (SS-319) at 11-30N 109-06E. The escorts counterattack dropping 65 depth charges, but are unsuccessful. At 1900, the convoy seeks refuge in Nha Trang Bay, Indochina.
23 February 1945:
In the morning, departs Nha Trang Bay. At 1210, YAKU is torpedoed and sunk by LtCdr George H. Laird's USS HAMMERHEAD (SS-364) at 12-44N, 109-29E. CO, LtCdr Mitsui, and 132 crewmen are KIA. LtCdr Mitsui is posthumously promoted Cdr.
10 April 1945:
Removed from the Navy List.
 Sources vary as to the identity of the escort, i.e. YAKU or YASHIRO. The names share the same Japanese prefix character, only the suffix character is different. We have chosen YAKU in our kaibokan coverage, but realistically, it could be either ship.
Thanks for assistance go to Dr. Higuchi Tatsuhiro of Japan and Mr. Gilbert Casse of France. Thanks also go to Mr. Aki of Japan and Matthew Jones of Ohio for help in identifying kaibokan COs.
-Bob Hackett, Sander Kingsepp and Peter Cundall