[sarasi]

I have lived in Tokyo for 10 years and never seen a gejigeji in the city, but you might find them in parks, along with spiders etc. Gejigeji are harmless anyway. Mukade are worse, but the only mukade I have seen in central Tokyo was very dead. Hornets only if you are really unlucky. Basically you will get a similar number of insects in the city here as you do in cities in Holland- see many there? Mosquitos will be more of a worry if you come in summer.

I second the above, noooo, don't try to learn Japanese from watching anime- unsurprisingly, people do not speak like that in real life. That would be like only learning English from the Simpsons and South Park. The more Japanese you know the more you will get out of the trip, so if you have time, by all means take a basic Japanese course.

In Roppongi you might well get carded, and I disagree that alcohol vending machines are everywhere- they are increasingly rare, and the ones that are left often want you to scan your driver's license before you can buy anything.

Large supermarkets in the central city areas do tend to be a bit expensive because they are in upmarket department stores (usually basement). Convenience stores are a better bet, and those are everywhere.