Just got back from my Japan trip last week. Some tips to be shared, hope it's helpful for first timer visitors like me.
1. You can buy kit kat at Kansai Airport. I've manage to get 6-7 flavours in total. If can buy them inside the boarding area where all your bag scanning and passport verified. Prices inside there are cheaper by YEN180-200 per big box. I've also found Wasabi & Kobe Pudding flavour inside the small stores !
2. Royce can only be found inside the boarding area at Kansai Airport, and T2 if i remember correctly. However very few / limited choices found over there.
3. Noticed many Royce choices at Shin-Chitose airport. So buying there will be better. If you have chance, spend few hours shopping around Shin-Chitose airport, best airport to shop. Try their cheese cake brand "LeTAO" very nice. Too bad I can't bring back as the cake can only stand maximum 6hours ice packed.
4. JR train and stations are far more better than Nankai train and station. If you are like me who doesn't understand Japanese, Nankai train mostly don't translate the station English name, so you have to figure out yourself.
5. If you are dropping by Namba via Nankai, please do more research and map gathering. I got stuck in this station, so huge and not much english pointers available. The staff are either don't understand English at all or just a little bit. Try asking trespassers if you are lost at Namba Nankai station. Shinjuku JR station wasn't that hard as it shows very clear pointers and exits.
6. For first timers like me, don't worry too much on food. Generally any food you find there are quite OK and acceptable. Stores like K-mart, 7-11, lawson can always get food which can be suitable to our liking. I tried on foods which i can spot immediately at the street and also foods recommended by Regent found in page1. All are delicious

7. It's very important for first timer to rent a MIFI device in my opinion. You won't get lost easily via Google Map and you can always refer to Hyperdia if you are travelling by train. In case you missed some trains / or arrived earlier you can always check online. However, if you are travelling somewhere more urban with lesser internet coverage, it's better to plan or manage your next location in advance with internet coverage area first.
8. Don't expect yourself to check out late from hotel. In my trip, i mostly travel around 5-6am to catch up early trains. Arriving stations earlier than what you've scheduled (allow 20-30minutes from train departure) also helps you not to miss out the actual boarding place of the train. And best of all no need to be sardine packed during their peak hours. You can take your rest in the train, quite comfortable compared to our local trains.
9. I think it's wiser to get the Hokkaido expressway discount card or something like that. I was offered when i rent a car with Nissan. But i didn't take it and end up paying hefty amount of toll. Please check with the car rental company. I think it's not the normal ETC card.
10. If you are driving at Hokkaido, get both mapcode and telephone number for the places you interested to go for better accuracy. The English GPS in Nissan works very well with Mapcode and telephone numbers. I hardly relied on my Google Maps with the English GPS in my rental Nissan car.
11. Try to pump self service petrol at Hokkaido to get cheaper rate (Yellow colours logo). Fuels like Shell, Idemitsu, Eneos etc tends to be more expensive. Not too difficult to self pump, just put YEN10000 into the machine as deposit, pump and get your refund from the refund machine.
12. Drink plenty of waters. You can buy big bottles water from convenience store less than YEN100. Or you can drink their green tea or rice tea. Best of all, beers as well.

I also noted you can straight refill your water from your hotel's bathroom tap. It's clearly written there safe to drink. So just buy 1-2 big and small bottles and refill when you're back to your hotel.
That's all I can think off now. Hope this is helpful for first timers like me

PS: Special thanks given to Bro Sacwoc and Bro Regent for all the helps given. Not to forget other bro's who has given their inputs as well !