I also recommend going to Kansai first and making your way back to Tokyo.

I also think that, for the first-timer in Jpn, Kyoto is probably a better place to start out than Tokyo in terms of easing your way into how things work in Jpn and not being overwhelmed. Then once you get used to things (eg, transport, finding food, signs, etc), then you'll probably be able to get more out of your time in Tokyo and appreciate it more instead of being overwhelmed by it.