Why don't you combine Osaka and Kyoto together first since you're in the same region, can save on transport by using Kansai Thru Pass (you save some money if you go further day trips to Himeji & Kobe, other than Kyoto and Osaka), and go Tokyo at the beginning or at the end. Kyoto - can buy 1-day bus pass for 500 yen, save a lot and you walk less, compared to subway. Only drawback is, you have to spend slightly more time travelling due to traffic sometimes. For Osaka - can take subway. Back in May, I was staying at Kyoto, air bnb, very cheap and clean room - can definitely explore air bnb option if you want to save on accomodation. Don't stinge on food, lots of good food everywhere.

Take the willer bus express for overnight travel. was actually recommended previously and it's actually comfy for the most expensive type, 1 row has 2 seating + 1 seating. (think it was 10k or so for 1-way)
(be on time, as the bus is actually punctual)

I didnt use JR pass, tokyo was mainly using normal suica / icoca pass? can't remember.. Save money on the transport & accomodation, spend more on food and whiskey

Nice! Even extend to 13 days, for osaka / kyoto + tokyo is just touching the surface. I spent 2 weekends in tokyo, and 6 days for kyoto / osaka + day trip to universal studio, kobe + himeji. If anything, research way ahead on places to go and you can start planning on your routes using google maps. Their train and bus system is updated very accurately on google maps real time, so it's actually very useful when you plan ahead and can put it to use.

I'm already planning to go back next year, but probably do tokyo + hokkaido!

There is an elevated train, and it prolly costs you a few hundred yen. Walking is also ok provided it's not too hot or cold. Google map it and it shows you the cost, think should be 3 or 4 stops.

Actually, if you buy at airport for liquor, then they will seal it and you can bring into the plane.

For duty free stuff that you buy, you can actually unwrap and put inside your luggage..As long as you dont consume them, which they dont really check. Unless you're really unlucky hehe. Your receipt will be stapled onto the passport. Even i think, in the event they do check, as long as you didnt consume it, it should be fine. Meaning all your tax free items can be in a separate bag.

Whatever you check in and bring back is up to you, just that if you play it cool and walk through KLIA without getting scanned then no issue lah Of course not drugs or illegal stuff, i brought back lots of alcohol on my recent trip in May, if get taxed i'll cry

Also, to maximize your loots, fly ANA coz they allow 2 bags of 20kg each! Totally worth it, good service, good food as well. Airfare was about 1.3k return but that's right after peak period which is mid of May.

For those who are looking for pocket wifi, try Ninja Wifi, they have some promotions once in a while and it's pretty decent. 2 of us shared the pocket device and it could last a whole day, we didnt stream movies, just use it for surfing and google maps. I paid RM264 for 10 days, because they had a promo code if you fly ANA back then.

Hehe yes, i think better listen to sacwoc, as you wouldn't want us quoting you to break the law. Do whatever that makes you feel comfortable.