I imagine (I haven't seen it yet), that the Indian Ocean is for some odd reason positively teeming with the IJN even though after the carrier raids in March/April, 1942, there were virtually zero IJN ships in the Indian Ocean (yeah, a few small ships and maybe a CA/CL now and again).
So if the U-boats call for IJN help and see much more than a ratty old subchaser or Minekaze Class DD, it's serious fantasy.
tater