Pleasure, 3 weeks so any tips from you guys are welcome. I'll drop our Japanese friend a PM.
I hope it's not too late : I did a trip to japan last automn.
There are also many taito game center in all the mains quarters of Tokyo (shinjuku, akihabara, asakusa, shibuya, ueno)

the one from akiba. Impossible to miss it.
In facts you don't really need to look for game center as they are plenty of them. More difficult is to find "root" rooms, with real oldies of the 80ie. Moreover, Credits there are usually cheaper : Y50 insted of Y100
Don't miss to go to Namco tower in Kyoto


Even if it isn't a "top notch" game center, there are many rare cabs there.
Advices for gaidjins :
1. Don't be afraid to ask for your path in the subway, the guards there usually speaks a bit english. Sometimes, some stations don't display western fonts.
2. Usually, coin operated machines, like those in the subway or in ramen shops, works after you put money inside. It seems obsvious now but especially with screen operated machine, we are used to choose what we want and pay after.
3. For arcade shops, you should have a good obstinacy to find them. They are often hidden in the stairs of the buildings.
The only clues are some things like this on the ground floor :

Looking at the mailbox :

By the way, people in these shops don't speak a single word of english.
It might also be a general rule for whole japan.
So if you are looking for some precises things, prepare a printed list in katana fonts.
You'll be lucky if you find someone speaking english.
Arcade stores : mak, gfront, try
4. Have no hesitations to by used thnigs, there are many shops for this, it's always in almost perfect condition.
Used stuffs shops : Traders, mandarake, Mr Potatoe.
And as always, don't hesistate to climb in the stairs, You may fall on very interesting shops.
I remember one at the beginning of akihabara, selling xrgb upscaler.
5. For brand new Gears, Have no hesitation by buying in duty free, the shop should be allowing it (like Yodobashi camera in akiba)
Addtitional Tip : Last, but most important : 7 Eleven stores have Automatic Cash Dealer (ATM) that takes Visa card.
Apart from several selected banks, this is the only easy way to get cash over there.
It's by far the best way to get money, as 7 Eleven are almost always open and they are everywhere.
I recommend All Nippon Airlines (ANA) as service is top notch for an affordable price.