From: Hessen, Germany - now living in France
Puhis is right, the cargo missions to Europe are totally different from the supply runs in the Pacific.
Here is some interesting info from the Nihon Kaigun website about I-1:
Late August to early September 1942:
Yokosuka Navy Yard. I-1 is converted to carry a special 46-ft waterproofed Daihatsu-type landing barge mounted abaft the conning tower. Her 5.5-in aft deck gun is landed. I-1 commences joint exercises with the No. 4 Maizuru SNLF detachment designated as Special Landing Unit (S-Tokuriku) for a planned raid on Espiritu Santo, New Hebrides.
22 September 1942:
Arrives at Rabaul.
1 October 1942:
At 1830, departs Rabaul for a supply run to Goodenough Island, D’Entrecasteaux archipelago. I-1 carrys a Daihatsu landing barge and its three-strong crew along with a cargo of food and ammunition intended for the stranded survivors of Cdr Tsukioka Torashige's No. 5 Sasebo SNLF .
3 October 1942:
At 2240, I-1 surfaces off Kilia Mission on the SW tip of Goodenough Island. After contacting the survivors, the landing barge delivers its cargo, embarking 71 wounded and the ashes of 13 SNLF marines, then departs for Rabaul.
6 October 1942:
At 1330, I-1 arrives at Rabaul, where her passengers are debarked.
11 October 1942:
Departs Rabaul for her second supply run to Goodenough Island, carrying a fresh cargo of food and ammunition.
13 October 1942:
At 1830, I-1 surfaces off Kilia, contacts the Japanese garrison and launches her barge. A Lockheed "Hudson" Mk. IIIA patrol bomber of RAAF No. 32 Sqadron, alerted by Allied intelligence, sweeps over the landing area and drops flares and bombs. Considering his mission compromised, Cdr Ankyu dives I-1 and departs the area, leaving his barge behind.
14 October 1942:
At dawn, a floatplane from I-7 conducts a recce flight over Espiritu Santo and confirms the presence of several warships. The approaches to the harbor are found to be regularly patrolled. The Combined Fleet staff decides to cancel the raid on the base.
20 January 1943:
At 0730, arrives at Rabaul. Begins preparations for a supply run to Guadalcanal. Embarks a cargo of food in rubber containers (two-day rations for 3,000 men), most of which is stowed inside the submarine.