Japan itinerary - 8 to 10 days

Sumo. It's special. There is a grand tournament March 14-28 in Osaka. Maybe you can incorporate that somewhere into your trip. I saw it in Tokyo as part of a tour that included lunch and a visit to the stadium to watch the upper level wrestlers in the afternoon. It was great to have someone there who could help explain what was going on.

I have been to Japan once and that was to take a cruise.

I pre-cruised in Yokohama for a few days before sailing. I really liked Yokohama although because it is so close to Tokyo, many tourists choose to stay in Tokyo and skip Yokohama.

Would you consider a cruise? Many cruise lines offer cruises around Japan. The itineraries are always excellent.

Although I sailed Norwegian, i suggest that you do your own research.

Have you looked at any guide books yet? Do you know where you might fly to? Japan is a long country and there are huge variations in weather, especially at that time of the year. If you are in the north you could well encounter snow and cold temperatures

I went in October, flew into Osaka and immediately took the train to Kyoto where we stayed for four days. Stayed in a small somewhat traditional guest house near Kyoto station, very quiet and comfortable but we did not have access to our room between 10am and 5pm. Luckily weather was good so not a problem, Kyoto is an interesting mix of old and new, temples, cherry blossoms - you will be too early for them, skyscrapers, small. Wooden houses, beautiful gardens, and chaotic traffic. Lots of interesting places near the city, the Bamboo forest and adjacent temples and gardens and the Fushimi Inari Tanisha shrine with its hundreds of traditional gates - stunning.We unfortunately never made it to the old geisha district.

We spent a couple of days in Kurasinki where there is an interesting old town and a wonderful old wooden “castle” or pagoda, not sure which as it was not open and signage was in Japanese only. Here we stayed at a hotel operated by the Dormy chain. Good value, nice rooms, pleasant restaurant, and an onsen for a relaxing soak after a busy day of sightseeing, and also laundry facilities.

For the vegetarians, please note that many Japanese recipes use dashi, which is a fish-based stock. I recommend looking at happycow.net, which is an international vegan restaurant finder (also an app).

We love Japan, the people are friendly, the food is great and there is much to see there.
Suggest minimum of three nights in Tokyo, one more if you take a day trip north to Nikko.
Then take the Shinkansen to Kyoto:
The Tokyo - Kyoto Shinkansen trains are renowned for their exceptional punctuality and extensive schedule, offering up to 31 daily departures. This makes train travel one of the most convenient and reliable ways to navigate between the bustling city centers of Tokyo and Kyoto.

Spend at least three days in Kyoto to tour as many of the famous sites as possible:
https://www.tripadvisor.com/Attractions-g298564-Activities-zfr7917559-Kyoto_Kyoto_Prefecture_Kinki.html
If you have time, do a day trip to Nara to see the famous deer park.

I just can't resist this suggestion. Get an egg salad sandwich at a konbini (convenience store) which you will find all over Japan. Lawson, Family Mart and Seven-Eleven are the most common ones. And while your at it, pick up a fruit sandwich - I prefer strawberry but blueberry is also a winner). While this is not an entry requirement I almost feel it should be. And while I thought this was my own odd quirk, it turns out most of my friends who travel to Japan do this and even Anthony Bourdain had the same view.
https://www.foodie.com/2094961/anthony-bourdain-loved-japan-egg-sandwiches/

Enjoy your trip. I have become hopelessly addicted to traveling to Japan and usually go there two or three times a year. I am sure you will have a great experience.

@adgaliani, this guy seems to be fond of those sandwiches, also -
https://www.youtube.com/watch?v=v1LOiRfMc08

I see that no one seems to have mentioned hotels so thought I would add some input.

I prefer business hotels as they are relatively economical and offer very good value. Rooms are typically small though they all typically provide breakfast included with the room, wi-fi, various amenities (cotton swabs, razors, bath salts and such depending on the chain) are are often located near major train stations. We usually get a twin bed room as it is often a bit bigger than the most basic double room. I've paid less than US$60 a night in places less touristed while US$125 or thereabouts is more typical for Tokyo.
I like the breakfast buffets as it gives me a chance to try some things I would be hesitant to order as there is usually a decent variety of western and Japanese items. I have noticed the further you get from the main tourist areas, the smaller the choice of western options but there is always something.

A slight step up with bigger rooms would be places like Mitsui Garden Hotels or Tokyo Stay hotels. Tokyo Stay hotels typically have a washer dryer combo in each room so we often stay in one mid-way during our trip to take advantage of that.
JR Hotels are typically near the bigger JR stations and are nicer with larger rooms and bigger breakfast areas. I have stayed at the ones in Hakodate and Takamatsu and they had great views as they were the tallest buildings in their locations. Both had typical breakfasts as well as a breakfast sushi bar if that is something you might like.

Can't speak to any of the major chains like Marriott or Hilton as I usually avoid them.

You also mentioned a February/March time frame. I was in Hokkaido this past February and there was lots of snow and cold weather though that doesn't seem to stop visitors. Even with the weather there was plenty to do and Sapporo has an underground pedestrian network in the central area which makes it easy to get around there while being out of the cold. As an aside there are plenty of restaurants underground and I can confidently recommend the Danish Style French Toast served with maple syrup and Hokkaido ice cream. I tested it extensively.
We did have some weather disruptions and in northern Honshu opted out of our planned visit to Hirosaki as the train service was experiencing heavy delays and we did not want to get stranded.
Weather further south - Tokyo and western Honshu - would typically be milder.

Also, you might want to check for holidays. I thinking Feb 12 or thereabouts is Nation Day (or something like that) so more visitors and higher room rates.