Read up a bit on the WW2 Japanese doctrine. They fired torpedoes from long range, and if you didn't know to look out for them, that was your problem. Their DE, DD, CL and CA all had torpedo launchers, and most did not have radar until late, if at all. If nothing is supposed to be in a given area, when something is seen, it must be enemy. All target "ID" was visual, and a submarine on the surface does look like a DE or DD from long distance, hence, they shot torpedoes, probably assuming the "ship" was between 6 & 8k away. Gun engagement would follow at just about the same time as the expected torpedo hits. Here's an interesting article:
https://nationalinterest.org/blog/bu...d-war-ii-48887
There are more that describe their long-range and profligate use of torpedoes, and yes, they did hit themselves several times, and their "hit" percentage was generally quite low, with a few engagements off Guadalcanal showing the weapon's potential, but also spotlighting its mis-use... I often wonder how many more torpedoes were shot that US ships never saw because they had changed course with a zig or a zag after the shooting platform let fly? There is an article that studies that perspective, and is in the JANAC reports somewhere... their hit to miss ratio was quite poor, being worse than the early US Mark 14 ratio.
Edit: one thing in the game as it stands now with the use of the TorpGun, is that the DD will indeed use the weapon for AA fire also... so if you see airplanes attacking DD in the game, look-out for torpedoes to be sprayed in every direction. There will also be the inevitable fratricide incidents that way also... The "fix" is to make the guns from a Main gun weapon, but then they shoot torpedoes when you're 10k yards away... so a compromise has been done, and they are short-ranged weapons in FotRSU and TMO_BH.
PS: I found another example of the IJN use of torpedoes, though no details, from
H-Gram 068:
“'They Sold Their Lives Dearly' is the title of a Tom Freeman painting that hangs in the entrance to my office at Naval History and Heritage Command. The painting shows USS Houston under a deluge of shellfire, her own guns are blazing away as she is surrounded by an overwhelming Japanese force while attacking the Japanese invasion fleet off Java on the night of 28 February/1 March 1942. It took 87 Japanese torpedoes to put Houston and her consort, Australian light cruiser HMAS Perth, under, and in the chaotic melee, Japanese torpedoes sank four of their own troop transports."