Been thinking about your trip... honestly, I'm super happy I had a filter when I bumped into someone in a Shinjuku station rush.

• B+W 46mm XS-Pro Clear MRC-nano 010M Filter is great glass for protection. Much cheaper than the Leica E46 UVa II Filter which feels like overkill.
• Match Technical Boop-O-L Soft Release Button makes the shutter feel smoother. Don't buy cheap generic ones tho, they just fall off.

Honestly, keeping that M10 safe is priority one. I'm super happy with the Peak Design Slide Lite Camera Strap Black since it's more secure than the basic leather ones, even if it looks a bit modern. For storage, the SanDisk Extreme Pro 128GB SDXC UHS-I works well and is way more reliable than generic cards, though it's a bit pricier. No complaints tho, worth it for the peace of mind.

Building on the earlier suggestion about the battery, I've found the stock charger is a bit of a brick for travel. When I was shooting around Ginza last spring, I was super happy I switched to a USB setup. I use the Nitecore ULSL USB Charger for Leica BP-SCL5 because it gives you actual data on the battery health and charging voltage, which is huge for reliability when you're relying on one or two cells for the whole day. Quick tips for keeping things solid:

• Pick up an Expert Shield Glass Screen Protector for Leica M10 to handle the inevitable bumps in crowded subways.
• Get a high-quality half case like the Arte di Mano Half Case for Leica M10 because it adds a bit of grip without the bulk of a full handle. Honestly, the M10 is a tank but that rear screen is a total scratch magnet if you arent careful. I've had zero complaints with the Nitecore charger tho... being able to juice up the camera from a power bank while sitting in a cafe is basically a lifesaver when you're doing 20k steps a day. Just makes the whole technical side of things feel much more controlled.

Building on the earlier suggestion, I've found that a spare battery is non-negotiable for long days in Tokyo. That Leica BP-SCL5 Rechargeable Lithium-Ion Battery has been solid for years. Adding a Match Technical Thumbs Up EP-MX Thumb Grip also completely changed how the M10 feels in-hand. It makes the camera way more secure, which is basically essential for street shooting...

Wait, I just had a thought... are you planning on doing mostly fast street photography in the crowds or are you more into the slow, tripod-based landscape stuff at the shrines? That'll really change what kind of kit you'll want to lug around all day. I remember when I first got my M, I was so paranoid that I bought every official Leica add-on I could find because I thought they were the only ones that wouldn't break my camera. Honestly, it was a waste of money. The boutique brands people mentioned are usually just as good, sometimes even better designed. Just be careful with the super cheap generic stuff from random sellers tho. I once bought a cheap grip that didn't fit right and it actually scuffed my baseplate. Make sure to check that anything you buy is actually made specifically for the M10 and has good reviews from other M owners. Also, what's your budget looking like for these extras? Tokyo is expensive enough as it is, and you might want to save some cash for the actual trip instead of spending it all on gear you might not even like using yet. There are some killer camera shops in Ginza you might want to visit anyway...