(A Type 1TM Standard Tanker underway)
Tabular Record of Movement
© 2010-2018 Bob Hackett and Peter Cundall.
3 October 1942:
Aioi. Laid down at Harima Dockyard as a 5,280-ton Type 1TM Standard Tanker for the Mitsui Line.
Launched and named OTORISAN MARU.
10 May 1943:
20 May 1943:
Departs Moji in convoy No.158 also consisting of IJA transports NISSHO (6526 GRT), RYUYO, USSURI MARUs and KONAN MARU No. 1, IJN transport TARUSHIMA MARU, civilian tanker (C-AO) RONSAN MARU and one unidentified merchant ship escorted by destroyer SHIOKAZE. IJN requisitioned (B-AK) ATLANTIC MARU joins the convoy from Miike the same day.
23 May 1943:
OTORISAN MARU arrives at Takao in convoy No. 158 (first part) with NISSHO and USSURI MARUs and KONAN MARU No. 1.
26 May 1943:
At 0800 OTORISAN MARUs departs Takao in a convoy also consisting of NISSHO MARU (6526 grt) with an unknown escort.
2 June 1943:
At 1400 arrives at Singapore. Undergoes engine repairs and later departs for Palembang.
E 4 June 1943:
9 June 1943:
Departs Singapore in Kyokuyo Maru convoy also consisting of KYOKUYO and LONDON MARUs without escort.
12 June 1943:
Arrives at St Jacques.
13 June 1943:
Departs St Jacques in the "T" convoy consisting of ASAMA and OTORISAN MARUs escorted by destroyer KARUKAYA.
17 June 1943:
At 0500, OTORISAN MARU is detached from the convoy at 14-55N, 118-44E and sails for Manila.
18 June 1943:
At 2030 arrives at Manila.
6 July 1943:
OTORISAN MARU departs Manila for Singapore with TEIHOKU MARU (ex-Vichy French PERSEE).
15 July 1943:
Departs St Jacques in convoy No. 593 also consisting of TSUKIKAWA and KOKUEI MARU's and NICHINAN MARU (1945 GRT) without escort.
18 July 1943:
At 1630 arrives at Singapore.
19 July 1943:
At 1200 departs for Palembang.
2 August 1943:
At 1300 departs St Jacques for Takao in convoy No. 415 also consisting of SYDNEY, SEISHIN, KOKUEI, USSURI, GYOTEN, TSUYAMA, YAMAGATA, TAIAN MARUs and six unidentified merchant ships without escort. The convoy splits into two parts.
E 5 August 1943:
OTORISAN MARU is detached and sails to Hong Kong.
12 August 1943:
According to radio intercept unloading cargo at Kowloon.
26 August 1943:
28 August 1943:
At 1400 departs Singapore for Palembang.
1 September 1943:
Scheduled to depart Palembang.
4 September 1943:
15 September 1943:
At 1400 departs Medan with ARIAKE MARU for Singapore. Sails at 12 knots.
22 October 1943:
At 1100 departs Moji in second part of convoy No. 108 also consisting of SHINWA, KOSHU, TOTTORI, MADRAS, HASSHU, HEIMEI, SEATTLE MARUs, KYOEI MARU No. 7 and UNKAI MARU No. 12 and two unidentified merchant ships escorted by auxiliary gunboat CHOKAKUSAN MARU.
30 October 1943:
Arrives at Takao.
2 November 1943:
Departs Takao in convoy HI-17 also consisting of AKITSU, ASAMA, OMUROSAN, OTOWASAN, TATEKAWA, ITSUKUSHIMA, KACHIDOKI (ex American PRESIDENT HARRISON), SAKITO and TARAKAN MARUs and Naval gasoline tanker TAKASAKI escorted by destroyer FUYO and kaibokan MATSUWA and ETOROFU.
4 November 1943:
Arrives at Manila. AKITSU MARU and FUYO detach.
5 November 1943:
Departs Manila still in HI-17. FUYO joins as an additional escort.
6 November 1943:
At 1830 ETOROFU is detached from the convoy and begins a submarine hunt.
11 November 1943:
At 1000 arrives at Singapore.
13 November 1943:
8 December 1943:
Departs Inland Sea for Tokyo Bay in convoy 8208 escorted by auxiliary minesweeper SENYU MARU No.3.
21 December 1943:
OTORISAN MARU departs Moji in convoy HI-27 also consisting of KUNIKAWA MARU, cargo-passenger liners MIIKE and TSUKUSHI MARUs, cargo liner NOTO MARU, IJA landing craft depot ship MAYASAN MARU and oiler KYUEI MARU escorted by destroyer ASAKAZE. NOTO MARU carries the 72nd Field AA Battalion, 14th Shipping Eng Regiment and she and the convoy also carry the 1st echelon of the 53rd Division consisting of Div Hq, 53rd Div, 128th Infantry Regiment and div troops (including comms, transportation, veterinary, supply, maintenance etc.), 234th Naval Construction Unit, 43rd Independent Field AAA Company, 46th Field Ops Machine Cannon Company, 47th Field Ops Machine Cannon Company and 12th Independent Searchlight Company.
24 December 1943:
Arrives at Takao, Formosa.
26 December 1943:
Departs Takao for Singapore with a replacement escort, kaibokan MATSUWA. The convoy now only consists of OTORISAN, KUNIKAWA, TSUKUSHI and KYUEI MARUs; the others remain at Takao.
27 December 1943:
At about 1100, in the second of two submerged attacks, LtCdr (later Captain) Robert D. Risser's (USNA ’34) USS FLYING FISH (SS-229) successfully torpedoes and sinks tanker KYUEI MARU at 21-25N, 118-05E. 54 crewmen are KIA. MATSUWA rescues survivors and the ships continue their voyage.
2 January 1944:
Arrives at Singapore.
8 January 1944:
At 0800 departs Singapore in convoy HI-28 also consisting of tanker SARAWAK MARUs escorted by Kaibokan MATSUWA.
17 January 1944:
At 2240, arrives at Moji.
1 February 1944:
At 1500 OTORISAN MARU departs Shanghai.
3 February 1944:
At 1300 due to arrive at Takao.
14 March 1944:
At Osaka undergoes compass adjustment.
19 March 1944:
OTORISAN MARU departs Moji for Singapore in convoy HI-55 also consisting of RYOEI, KACHIDOKI (ex US -PRESIDENT HARRISON), ASANAGI, TARAKAN, KAGU and TENSHIN MARUs and five unidentified ships escorted by destroyer HARUKAZE.
24 March 1944:
The convoy arrives at Takao. The six unidentified ships and destroyer HARUKAZE are detached. She is replaced by kaibokan MATSUWA and torpedo boat HATO.
26 March 1944:
OTORISAN MARU departs Takao in the convoy also consisting of RYOEI, KACHIDOKI (ex-PRESIDENT HARRISON), ASANAGI, TARAKAN and TENSHIN MARUs escorted by kaibokan MATSUWA and torpedo boat HATO. Soon after departure RYOEI and TENSHIN MARUs develop unknown problems and return to Takao.
2 April 1944:
At 1900, the remainder of the convoy arrives at Singapore.
8 April 1944:
Departs Singapore in Convoy HI-56 also consisting of tankers ASANAGI and SARAWAK MARUs, NICHINAN MARU No.2 and two unidentified merchant ships escorted by destroyer KURETAKE, torpedo boat HATO and Kaibokan MATSUWA.
11 April 1944:
Arrives at St Jacques and merges with convoy HI-54 then consisting of NANKAI, ARIMASAN, KYOKUHO and MIRI MARUs escorted by kaibokan AWAJI.
14 April 1944:
At 0800, departs St Jacques.
19 April 1944:
Arrives at Takao.
24 April 1944:
Arrives at Moji.
3 May 1944:
At 0445, OTORISAN MARU departs Moji in convoy HI-61 also consisting of empty oilers TATEKAWA, NICHIEI, JINEI, EIYO, AZUSA, AKANE, SARAWAK and ASANAGI MARUs and fleet oiler HAYASUI, passenger cargo ship MIZUHO MARU escorted by escort carrier TAIYO, destroyers ASAGAO, HIBIKI and INAZUMA, kaibokan SADO, KURAHASHI, CD-5, CD-7 and CD-13. 
7 May 1944:
JINEI MARU is detached because of engine trouble.
8 May 1944:
About 0615, LtCdr Victor B. McCrae's (USNA ’32) USS HOE (SS-258) attacks the convoy at 19-19N, 120-00E. In a submerged attack, McCrae fires all his bow torpedoes and gets a single hit on AKANE MARU. She is detached from the convoy and returns to Takao, Formosa for repairs.
9 May 1944:
At 2055, the remainder of the convoy arrives at Manila.
12 May 1944:
The remaining six ships of the convoy depart Manila.
17 May 1944:
At 2100, arrives at Singapore.
23 May 1944:
At 0700, OTORISAN MARU departs Singapore for Moji in convoy HI-62 consisting of transports KINUGASA, NOSHIRO, NISSHO, TAMATSU and TEIRITSU (ex-French LECONTE de LISLE) MARUs and tankers SARAWAK and NICHINAN (5175 gt) MARUs escorted by escort carrier TAIYO and kaibokan KURAHASHI, SADO, CD-5, CD-7 and CD-13.
29 May 1944:
HI-62 arrives at Manila.
1 June 1944:
At 0400, HI-62 departs Manila. TAIYO continues to provide antisubmarine air cover.
CD-7 detaches from HI-62.
8 June 1944:
Arrives at Mutsure anchorage, then proceeds to Moji arriving at 0230.
20 June 1944:
At 1930, OTORISAN MARU departs Moji for Singapore in convoy HI-67 also consisting of transports GOKOKU, MANJU, NANKAI, KINUGASA, ASAKA, ASAHISAN and HAKOZAKI MARUs and oilers MIRI, NICHINAN No. 2, SARAWAK and SHINEI MARUs escorted by destroyer KURETAKE, minelayer SHIRATAKA and kaibokan HIRADO, KURAHASHI, CD-5, CD-13 and subchaser CH-61.
E 26 June 1944:
Destroyer ASAGAO and kaibokan CD-2 join convoy HI-67.
29 June 1944:
Near dawn, LtCdr (later Captain) Anton W. Gallaher's (USNA ’33) USS BANG (SS-385) picks up convoy HI-67. Gallaher makes a long "end-around" in daylight. At about 1500, he fires all ten torpedoes in his bow and stern tubes at three ships. He damages MIRI and SARAWAK MARUs. Both oilers are hit in the bow, but each manages to proceed to Manila.
30 June 1944:
The convoy arrives at Manila. GOKOKU, SARAWAK and MIRI MARUs are detached.
3 July 1944:
At 0600, HI-67 departs Manila.
9 July 1944:
Arrives at Singapore at 1640.
14 July 1944:
At 0730, convoy HI-68 departs Singapore via Manila for Moji. The convoy initially consists of tankers OTORISAN, TOA, SHIMPO and TOHO MARUs and NICHINAN MARU No. 2 and transports KIYOKAWA and MANILA MARUs escorted by minelayer SHIRATAKA and kaibokan KURAHASHI, HIRADO and CD-13, CD-20 and CD-28. OTORISAN MARU carries 9,000-tons of gasoline.
E 18 July 1944:
SHIRATAKA is detached from the convoy.
20 July 1944:
At 1300, arrives at Manila. Later that same day, KURAHASHI is detached to go to the aid of light cruiser OI, torpedoed the previous day by USS FLASHER (SS-249) at 13-12N, 114-52E. KURAHASHI returns to
Manila the next day.
24 July 1944:
HI-68 departs Manila at 0600 for Moji. The convoy is expanded to 14 ships to include some ships previously from the Manila leg of HI-69 and MOMA-01.
The convoy sails in three columns consisting of merchant tanker OTORISAN MARU and tankers NICHINAN MARU No. 2, IJA landing craft depot depot ship MAYASAN MARU and escort carrier TAIYO in column no. 1; IJA lLanding craft depot ship TAMATSU MARU and transports TOSAN, KASHII, NISSHO and AKI MARUs in column no. 2 and transport KIYOKAWA MARU and tankers TOA, TOHO, SHIMPO and ITSUKUSHIMA MARU in column no. 3.
The escorts include carrier KAIYO, kaibokan HIRADO (F), KURAHASHI, ISHIGAKI, KUSAGAKI, MIKURA, CD-11 and CD-20 and torpedo boat HIYODORI.
The ships sail at 11.5 knots, the average speed for HI series convoys. A three-submarine wolf pack of Cdr (later Rear Admiral) Rueben T. Whitaker’s (USNA ’34) USS FLASHER (SS-249), LtCdr Franklin Hess’s (USNA ’35) USS ANGLER (SS-240) and LtCdr Francis D. Walker’s (USNA ’35) USS CREVALLE (SS-291) attacks the convoy.
25 July 1944:
Off NW Luzon. At 1540, transports AKI and TOSAN MARUs succesfully evade an attack by USS CREVALLE.
26 July 1944:
Off Luzon. At 0211, in a night surface radar attack, USS FLASHER closes first. Cdr Whitaker fires three torpedoes at AKI MARU and his last three torpedoes at OTORISAN MARU. One torpedo hits AKI MARU amidships, another strays and hits TOSAN MARU. OTORISAN MARU blows up and illuminates the night.
USS FLASHER sinks OTORISAN, TOSAN and AKI MARUs. 46 men aboard OTORISAN MARU are KIA. On AKI MARU some 24 passengers were killed as were 14 ship’s gunners, and 3 crew; a total of 41 dead. 
 OTORISAN MARU was under civilian control at the time of her loss. Earlier in the war, she made charter voyages for the Imperial Army as
Army No. 5048.
Thanks to Gilbert Casse of France.
- Bob Hackett and Peter Cundall.
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