Electras are great bikes, if they're comfortable for you. I didn't really like them, but my wife has had two in the past.
I don't know what the terrain is like in Tokyo - I'm assuming it's mostly relatively flat there, but I've never actually spent any time there. All my time in Japan was spent in Kansai - in and around Osaka prefecture. I had a mountain bike, which comfortable to ride in Japan. Although you're probably better off with a hybrid that has road tires - pretty much the only time I got off of pavement and concrete was at entrances to shrines and temples. I've never been a very accomplished bike rider but because of the hills, if I'd had a bike with only a single gear I would have spent a decent amount of time pushing my bike. I know the mamacharis don't look cool, but I knew a guy that biked up Mount Koya on one. So they're definitely enough to get you around. I did it on a mountain bike and it was so much fun.