Translate JP reservation sites on a computer with Google Chrome using the translate button next to the URL. You may need to switch back and forth between English/native language and Japanese to get successive drop downs to populate in English/native language. Most sites also don't like accepting the date in Translated mode so be sure to set it while in JP. You can register for a JP Rakuten account in English https://grp01.id.rakuten.co.jp/rms/n...service_id=top which will make sure the reservation is for the same Roman name as shown on an IDP- the same account works for a myriad of Rakuten JP services including JP food delivery.

Tabirai.net is also worth a look sometimes - their rates usually bundle in a CDW if you were going to opt for that & sometimes optional 24h NOC waiver is cheaper, too. It is also a JP rental car consolidator like Rakuten and Jalan. English options/available packages are more expensive than the JP options but likely cheaper than something like rentalcars.net. The English site also has CDW options in English Information regarding insurance and CDW | Tabirai Japan Car Rental