It seems the IJN did have operational (and effective) radar from 1943 on, but it was inferior to US radar.
Generally it seems to me the IJN became gradually more effective in ASW during WW2, but could not capitalize on this experience in 1944 because of the general slaughter that ensued on land and in carrier battles.
Similarly to the italians, who totally bungled ASW in 1940/41 but got quite good at it in 1943.
Keep in mind most USN subs were lost in 43/44, and losses to planes only started in 1944/45 when the IJN apparently had airplane based radar.
Sadly SH4 has totally useless river gunboats, but no Ukuru class escort ship or Tomozuru class torpedo boat.
Regarding the CVs, the regular scouting duty done by VS squadrons in the USN was done by the carrier attack planes in the IJN. The Aichi D3A (Val) dive bomber was awkward to handle on carriers since it had non folding wings. The B5N (Kate) torpedo bomber had better range, DF equipment and a third crewmember to help with navigation. At least on approach to midway, one carrier always had flying duty comprised of attack planes on ASW patrol.
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