Karting in Tokyo

I want to reserve a slot for karting in Tokyo. I'm thinking doing a 2 hour course or maybe 3 hours, preferably from Akihabara.

Where's the best place to purchase tickets online that offers good value for money?

I don't know what you mean by "karting" around Tokyo. But if you mean those dreadful machines with people in costumes, then here's one: https://kart.st/en/tokyobay.html

Please rethink this. You will be a in a tiny go-kart on busy city roads. You will be far lower than the rest of the traffic, potentially out of sight of large vehicles such as trucks, without the safety of a car frame around you and often no helmet. You will receive little safety training. You will be a hazard and nuisance to locals just going about their days. It's only a matter of time before someone is seriously injured or killed in these activities.

If you wouldn't want go-karts zipping around you when you're trying to drive to work, and wouldn't ride a go-kart on the busiest road you can think of, don't do it.

�gIf you wouldn't want go-karts zipping around you when you're trying to drive to work�h

This is what it boils down to for me. The whole business is having tourists behaving badly.

It's only a matter of time before someone is seriously injured
Lots of accidents already reported - a couple serious. They seem to be having an accident one per week.
Make sure you have good travel insurance.