Thank you so much. I will tackle this when I get back on Monday, I am traveling all weekend. Hope I can get a booking sorted immediately. I will go through Rakuten as you said (but first I will scroll up here in the thread to remind myself what Rakuten is).

EDIT - At the cars section of Rakuten Travel, it says "brought to you by rentalcars.com"! So it is an aggregator then. I could just book it using rentalcars.com, no? It took me a while to find an English language page for Rakuten and it's a bit challenging (and annoying) trying to do it on a mobile phone. I can't even read the tiny logos of the unfamiliar rental car companies, so I will wait until I am home on Monday and do it on the computer.