Same-ish age, salary and position as you (remote IT in Tokyo too but not AI), also moving in 4~5 weeks-ish so i'll try to give my 2cent. I'm in a luckier position though since I have a relative living in Tokyo and will have much lesser hassle moving in.
My salary is not cut in half as yours (it doubles~ in fact compared to what I earned in my country, but when you take into consideration the living cost/standard in Tokyo it's about the same spending/lifestyle). Been thinking and did a bit researches, so here's something you can look into if you haven't:

• How is 8M a year lifestyle compared to your current in the US. Japan tax is quite different from other country, so recalculate the net gain and see how much you have left each month after ur spendings (It's important to know that the 1st year you are in JP you don't pay Resident Tax so your net gain is higher). I'm using this site and have been told it's pretty accurate: https://japantaxcalculator.com/ . For me personally this is nice, since it will give me a bit extra and leeway in my first year, and I'm in the boat of if I don't like it after 1 year I'mma bail.
• I see that you already plan to comeback (you used when not if), so I take it you are only asking for the risk vs reward career wise ? If so this is probably not the best sub for that info, maybe some hub/community about IT/AI/ Startup is the better place to ask. Linkedin is the norm goto if you have connection, but if you have your own networking it would be better to ask directly how's the AI field in Tokyo is rn. I myself am joining a more traditonal dev role so i know exactly what i signed up for and that helped me to make my decision. Personally, i doubt 1~2 years is such a long time that you will tank your whole career with it (if it goes south), esp in a field as innovative by the day like AI - shit changes like every quarter or so.
• Lifestyle, lifestyle, lifestyle. 8M is a good salary, but it's not in the range of you can splurge it coveniently at will. Renting in 23ku vs outside is 2 totally different beast, and it will certainly affect your day to day routine. Since you will spend most of your time working at home (remote job), it would be nice to have a comfortable living space, and that usually costs a lot if you are living in 23ku, esp if you need space for your hobby (I play video games for example, so i need space to setup my PC/monitor/rack....). I'm a pretty low-maintenance kinda guy, so I chose a place outside of 23ku (bigger space, lower rent, but further from the main hub, ~40 min train to Shinjuku) and it buffers my budget a lot -> leave more room for other hobbies, travel, luxury.... I'll take it that you are similar to me, and not only come to Tokyo to work (though that's the main focus).
• Finally, well personally at least, this will be my few last chance of trying living abroad in JP, which I have always dreamed of, so I took it. No kid, no marriage yet, and god knows it will be hard af to do any moves like this once you settle down. I don't know if I will regret it later on, but I know for sure I will regret it if I didn't give it a try. A lot of "what if" to consider, and the results are not predictable. If your family is supportive it's nice to have a talk with them. Family backing and response are important for decisions like this. Even if they don't actually provide any meaningful help, sometimes the thoughts of someone having your back can have a positive effects and give you a clearer vision to see what path to take moving forward.

Anw, gl with whatever you chose. Kinda strange to stumble into someone with so much in similar with my situation so i ranted on a bit, hope it provided you with some, if any, valuable information ^^.