smart plugs flashable with tasmota firmware would be ideal, https://templates.blakadder.com/jp.html has a list of compatible devices for Japan. Unfortunately, mostly not available. I had found one of these and ordered from China, it never arrived.
via API from the cloud of the vendor, details. Changes in the consumption are reflected via API after up to 4 seconds. Difference of switchbot measured consumption versus measured in the system itself: 30%.
summary: offers functionality like remote on/off and consumption measurement only over the vendors cloud/mobile app. No APIs for automated reading available.
portscan: TCP/6668 open
model PS-P0P-W01/1P
functions direct API: no direct API
sniffing traffic, TLS1.2 encrypted connections to AWS are seen
ゴウサンド/Gosund WP6-1
summary: offers functionality like remote on/off and consumption measurement only over the vendors cloud/mobile app. No APIs for automated reading available.
ESPhome firmware supports the US version of the WP6.. no note about JP version.
I suspected this to be a Tuya device, but when I reset the plug and try to set it up with the Tuya app, it's not found. I had run through setup issues with tuyapi details, before concluding it's not Tuya compatible. tuya-convert is possible with Tuya devices.