Saw this post earlier but just now getting a chance to reply. Honestly, I had issues with finding cheap glass for my S5 too, the L-mount system is unfortunately not as good as expected for budget shooters. Everything is just so overpriced. I ended up picking up the Yongnuo YN 50mm f1.8 DF DSM L-mount last year for around $280 because I was desperate for a cheap AF prime for video. The autofocus is actually pretty decent, though the S5's contrast-based system still pulses occasionally. It is probably your best bet under $400 if you need autofocus. Another route is going manual, but for street video in Japan you're gonna want that AF working.

Yeah, unfortunately the autofocus on the S5 is pretty notorious for pulsing, and the Panasonic Lumix S 50mm f1.8 L-mount is not as good as expected for video tracking on that older contrast-detect system. It is frustrating because L-mount glass is generally so expensive. I had similar issues and ended up looking at these budget alternatives:

• Sigma 45mm f2.8 DG DN Contemporary L-mount
• You can easily find this used for under $250. The f2.8 limit is disappointing for night street shots, but it is tiny, light, and the AF motor handles video panning much smoother than the Panasonic primes.
• Panasonic Lumix S 35mm f1.8 L-mount
• If you search used markets like MPB, you can grab this for around $380. The wider focal length is way better for street and it hunts slightly less than the 50mm. Let me know if you want me to help you scout some reliable used gear sites to find a deal before your trip.

I almost lost a gig using primes on the S5. You might want to consider:

• Panasonic Lumix S 20-60mm f3.5-5.6 L-mount Just don't expect miracles in low light.

Regarding what #3 said about Saw this post earlier but just now getting a chance to reply, it honestly took me back to my first trip to Osaka back in the day. I was lugging around this massive, heavy kit bag that basically felt like a sack of bricks. I was so worried about having the perfect gear that I ended up spending half my time in the hotel room cleaning sensors instead of actually hitting the streets for ramen. My cousin tagged along and he brought this tiny, beaten-up camera that he basically bought at a pawn shop the day before we left. While I was stressed out about focus hunting and lens swaps, he was just having a blast, grabbing shots of literally everything. We ended up getting lost in a side alley near Dotonbori for like four hours, and I'm pretty sure I missed the best shot of the entire trip because I was fumbling with a lens cap in the dark. Gear obsession is such a rabbit hole, man. Sometimes I look back and just laugh at how much I overthought those specs.