There aren't many "Beyond Europe" trip reports on here for obvious reasons, but since the Japan thread is going on strong at the moment, I thought I would post a report of the 2-week trip to Japan my partner and I (early 30s) just went on in late Feb.
In a nutshell: it was AMAZING. Even though I had been to Japan before (twice, actually), it exceeded my expectations, and my partner (for whom Japan, and even Asia as a whole, was a first) was equally blown away.
Route
Day 1 : fly Paris - Osaka, head to Kyoto
Nights 1-4 : Kyoto, with a side trip to Nara
Nights 5-7 : Kusatsu Onsen in the mountains north of Tokyo, where friends who live in Tokyo joined us for 2 nights
Nights 8-10 : Tokyo (at our friends)
Nights 11-12 : Ryokan stay in Hakone
Night 13: Tokyo at our friends again
Night 14: flight back to Paris at 1 AM
Report
Weather, travel conditions, logistics, etc.
February weather was a concern of mine, but it was no worse than at home. Slightly better, in fact. Spring-like (but often rainy) in Kyoto, wintry blue skies in Tokyo, snow (barely below freezing) in the mountains north of Tokyo. Crowds were not an issue at all, and the plum trees were in full bloom. This was overall a much better experience than my previous trip in mid-August 2013...
Costs were pleasantly low thanks to the incredible exchange rate. Great coffee for 500 yen / $3.50, lunches for 1500-2000 yen / max $15, very nice dinners for $30/head and the max we spent was $60/head at a fancy restaurant booked for my birthday. This is overall 30-40% less than what I would spend in Paris.
The whole trip was planned exactly 2 months before departure: later than I like, but not a problem at that time of the year. We booked train tickets in advance to get to Kusatsu Onsen due to a holiday weekend (sales open 1 month ahead in Japan), as well as our hotels, 2 restaurants in Kyoto, and Teamlab Borderless in Tokyo. I tried unsuccessfully for the Ghibli Museum tickets.
Local travel was a breeze with stored-value cards (ICOCA) that we got from vending machines at Osaka-Kansai airport. Cash only for purchase and top-up, though.
We stayed connected thanks to Airalo eSims. Very cheap ($9 each for the trip!), very reliable, absolutely necessary for Google Translate and Google Maps. Although, regarding Google Translate, we needed it less than I thought. Many places had English menus, and many people we interacted with in stores, restaurants etc. had some basic grasp of English. Still, the ability to take a picture of something and get it translated immediately is a godsend.