> How with all those sensors could it not notice a tanker in the area? <
I don’t think the Japanese are at fault here. It’s more likely that those inscrutable ChiComs are now deploying stealth tankers.
A few years ago there were a couple of US destroyer collisions with other ships in that area. The bridge crew was relying on the radar that was set incorrectly.
Had they picked up their heads, and looked out the window with the Mark 1 eyeball they would have seen what they were running into.