I think we might need a bit more information.
The Japanese machines are usually Paschilo's they take "metals" which is the literal translation of token from Japanese to English.
There are about 100 different makers of these due to very little regulation. On the other hand many coin parts for North American machines are made by JCM - Japanese Coin Machine, or NCR, National Cash Register which also has Japanese ownership.
Does your glass on the machine say insert Metals ?? are you using Japanese tokens or north american coins ?
Theoretically gaming in Japan is illegal, so the max win on a Paschilo is 5:1, you play 3 metals and get a max of 15 returned. There however are bonus rounds which re-spin and automatically win 30 or so spins to make the real payout much more. I think the term they use translates to Fever mode.
Keeping with the illegal-ness of gambling you can only trade your metals for prizes. Ie a Giant stuffed Bear. When you walk out the door of the Paschilo parlor you will just happen to find a "prize redemption center" next door. Which of course is in no way related to the Paschilo parlor. Assuming the tag is still on the clear plastic bag holding the giant stuffed bear they just happen to want to buy it.
Generally speaking you buy 100 metals for $1000 yen - about the equivalent of about $10 usd, You would get a prize for 100 metals which you could sell at the redemption center for about 800 yen. Basically they make about 20% right off the get go.
Now with all that said, if what you have is a Pashilo - you might want to go to the Pachitalk web site.
www.pachitalk.com who specialize in Pashilos and Pachinkos.
You might also look for wireties or modifications - sometimes people would covert their .944 sized tokens to Quarters that are just slightly bigger by bending or wireting some of the parts. Again due to the sheer number of these units, and the need to always refresh these usually are mechanical mechs. The machines typically last <1yr in the pachilo parlor before they are sold off by the container to North America and Africa and replaced by newer themes.
Hope this info helps.