Regarding what #1 said about f/4, just bump the ISO. The Tamron 28-200mm f/2.8-5.6 Di III RXD is way more versatile.

• f/2.8 at 28mm
• 200mm reach Ngl, its the ultimate travel lens.

I learned the hard way that heavy glass ruins the mood in Tokyo. Lugging a massive setup through Shinjuku is just exhausting. You might want to consider the Sigma 28-70mm f/2.8 DG DN Contemporary instead.

• It's significantly lighter than the 24-105.
• The f/2.8 aperture is better for low light.
• It fits your $900 budget easily. Be careful with the lack of full weather sealing tho if it rains.

I spent a couple weeks wandering around Shinjuku and learned the hard way that a lens failing on you mid-trip is basically a nightmare. I was using a kit lens that got some moisture in it and it just stopped focusing... totally ruined my night. If you want something thats actually built like a tank and wont let you down, you might want to consider finding a used Sigma 24-70mm f/2.8 DG DN Art.

• Be careful with the weight tho. Its way heavier than the Tamron options and after walking 20k steps, youre definitely gonna feel it.
• Make sure to check the serial number to ensure its a later production model to avoid the old dust-intake issues some people had.
• I would suggest pairing it with a solid strap because the added bulk is real when youre squeezing through crowded subway stations. You can usually find these used for right around $850 to $900 if you shop around. Having that 24mm wide end is honestly a lifesaver for those big city shots where 28mm just feels too cramped... trust me, you'll want the extra room for those tall buildings.

Tokyo is gonna be awesome but honestly, picking just one lens is a massive headache. I had issues with the Sony FE 24-105mm f/4 G OSS specifically because that f/4 aperture is really not as good as expected when you are shooting in those dark Shibuya side streets at night. Its just too slow for low light without cranking the ISO until things look grainy... kinda disappointing for a lens that usually costs way over your 900 dollar limit anyway. If you want to stay under budget and keep your sanity, here is the reality:

• Tamron 28-75mm f/2.8 Di III VXD G2 is sharp but 28mm is frustratingly narrow for big city architecture.
• Tamron 28-200mm f/2.8-5.6 Di III RXD is my top pick for travel even though the build quality feels a bit cheap and plasticky compared to Sony glass.
• Sigma 28-70mm f/2.8 DG DN Contemporary is nice and light but unfortunately lacks that wide 24mm end you really want for travel. Tbh, I was pretty let down by most mid-range zooms until I tried the Tamron 28-200mm f/2.8-5.6 Di III RXD. Its not perfect and the variable aperture is kinda annoying sometimes, but for a one-lens trip to Japan, it saves you from the constant glass swapping. Just dont expect it to feel like a premium tank in your hand... it gets the job done tho.