10 day visit

I have few questions.

Suppose I visit for 10 days, how much food and train would I need to spend?

Could I go to Japan in December of this year if I just test negative for virus?

This page may help to get an idea for budget:
https://www.japan-guide.com/e/e2410.html

Regarding entry rules, if you are from a visa waiver country, tgen per current rules you can enter either with 3 covid shots or 1 negative covid pcr test 72 h before coming to japan. I am sure there is a page on JG that explains all this.

Enjoy planning your trip.

How much Food cost: It varies person to person.However my Favorite restaurant is sweets paradise.unlimited all you can eat 70 minutes cost 1390 yen @10 entry =13900 yen child=900 yen for 10 days all you can eat food

Train/rail journey cost also varies.but it is worth to spend.you can buy keisei rail 1 day pass=1500 yen or JR Thank you chiba free pass 2 day=3970 yen

It all depends on how cheaply you want to eat and how far and how fast you want to travel. You can easily spend 10 days just in Tokyo, eat all your meals from a combini and just get local type subway passes and keep your budget super low. If you want a JR Nationwide Rail Pass, want to travel all over the place for 10 days and eat a lot of multi course prix fixe meals, it is going to cost a lot more. If your budget is tight and you want to travel far there are always overnight buses. Though again, it would be very easy to find 10 days worth of things to do in Tokyo and environs or Osaka and environs.

It's like accommodations, I could pay over 1.25k USD to stay at the Park Hyatt for New Years or spend more like $47 USD to stay at the Toyoko Inn Toyoko Shinagawa Konan-guchi Tennozu Isle.

If you are going in December the week around New Years and New Years itself or more expensive than the beginning of the month and places are filling up.

I think the only part of the trip with less flexibility is airfare. The fare is what the fare is.