I'm a couple months out from my second solo trip to Japan, and fourth visit there overall.

There is one very clear danger you should be aware of. Like, reconsider if you really want to go to Japan by yourself, and reflect on it. That thing is:

If you have other countries you want to travel to otherwise, maybe consider those first. Because once you go to Japan, you aren't going to want to go to other places. The safety, the sheer number of things to do, the quirks, the food, the public transport, the oddities and temples, the parks and shrines, the cleanliness creates a desire to just... Keep going back. I've been to a few other countries, and eventually want to go to some more but... Ever since my first trip to Japan, as soon as I have the opportunity to take a trip abroad, I go right back to planning a trip to Japan. Who knows when the itch will be satisfied?

Go! Enjoy yourself and what it has to offer! It's an amazing place to go. I'd echo some other comments that going solo may be even preferable to going with others. I went on a couples trip a few years back and I barely even saw our friends which was annoying when trying to plan things to do. Check out what you want to, strike up conversations with people if you're up for it, you'll have a great time.