To add to the point above: honestly, I have to disagree with the notion that you need f1.4 for Shinjuku night shots. I've spent years shooting in Tokyo and people way overstate the need for ultra-fast glass because of how bright the neon signs actually are. Tbh, you'll probably find yourself stopping down anyway to keep the background lights from becoming just a blur.

• Flexibility is king in Japan. Those alleyways are cramped and you'll want the 18mm for scale, but then you'll see a detail on a temple that needs the 50mm reach.
• The Sigma 18-50mm f2.8 DC DN Contemporary Fujifilm X is insanely light, which really matters when youre walking 20k steps a day through Shibuya.
• Modern Fuji sensors handle ISO 3200 like a champ, so f2.8 isn't the handicap it used to be. Stick with the zoom for your first trip. Youll get way more keepers that way. If you really want a prime later, the Sigma 30mm f1.4 DC DN Contemporary Fujifilm X is usually cheaper than the 23mm anyway and is a killer low-light companion for the X-T30 ii.

@Reply #2 - good point! Flexibility is definitely huge in those narrow alleys, but honestly, I have had some issues with the autofocus reliability on these lately. It is just not as good as expected when things get busy or the light starts to drop in the evening. I was pretty disappointed with the build quality too... it feels a bit light and unfortunately lacks that solid feel you usually want for a heavy travel schedule. Since your budget is right around 500 dollars, I have a couple questions to narrow this down. Are you mostly shooting handheld or do you plan to bring a travel tripod for those night shots? Also, how much does weather resistance matter for your style? Tokyo is famous for those rainy street shots but unfortunately these specific lenses might not handle a downpour very well without some extra protection.

Jumping in here because I was in a similar spot last year. I spent way too much time obsessing over these two options before a big trip. Im still kinda new to this stuff though so take my advice with a grain of salt... but I think I remember reading that the zoom might have some issues with corner sharpness at the wider end? Not 100% sure but its something I’ve heard people mention in other threads. When I went to a crowded city with my fuji, I actually ended up struggling a bit with the decision. I chose a zoom because i was scared of missing shots but i found myself almost always stuck at one end anyway. Be careful about relying on that f2.8 at night in those narrow alleys. Shinjuku gets bright with all the neon but the shadows are super dark and I really felt the limitations of my slower glass back then. IIRC, some people say the f1.4 is a lifesaver for that specific vibe, but then you're stuck walking back and forth to frame things which is hard in crowds. I would suggest checking if the weight difference actually matters to you too. Make sure to consider how much you're gonna be walking. Tokyo is brutal on the feet and a heavy lens gets old fast. Honestly I'm still figuring out if I prefer the prime look myself... it’s a tough call. Just make sure to double check the weather sealing too, because if it rains in Tokyo, you might want to be careful with either of those since they might not handle a downpour well.