1. Does anybody have the link to a Tennokoe Bank Battery Replacement FAQ IN ENGLISH? (I don't read Japanese)
I don't have one, but it should be pretty straightforward: pry off the plastic cover, remove battery and replace with new, snap plastic cover back in place. Most likely the battery is soldered to flat metal leads, so care will be needed to ensure that nothing's damaged from heat while soldering/desoldering.
2. What is the designation of the little round battery inside the Tennokoe? (like for example CR2032 is the one inside the Sega Saturn)
a. I think it is CR2320, but I want to confirm that. Is this correct?
Just buy one and take a peak under the hood; it'll be much quicker than waiting eons for someone here to answer (I'd check my own but fear damaging a card that still works).
b. I wanted to replace the battery in the Tennokoe with the exact same battery (a Panasonic CR2320 I think) and I did a little searching for Panasonic CR2320 batteries, but all I could find is Panasonic BR2320 (B instead of C)
Anybody know if BR2320 and CR2320 are exactly the same battery?
I'm double checking this because I accidentally FRIED my Saturn by replacing the CR2032 battery in it (which is rechargable) with a DL2032 (which is NOT rechargable -_-)
It looks like you can get a Panny CR2320
here or
here. If you're not particular about the manufacturer, there's plenty of other sources that can provide a CR2320 battery from various manufacturers.
The difference between CR and BR type batteries is minimal (
Klicky VonKlickerson).
3. Finally, anybody know any reliable online stores where you can buy a Tennokoe Bank? (please list the one with the cheapest price you know of, I may buy 2 
Contact
Rising Stuff (run by fellow PCFXer Sensei). Mine came from Ebay; they're always littered with 'em.
