Kimura here, suffering from sudden heat exhaustion after returning from Hokkaido, where there was a temperature difference of about 15 degrees between Nagoya and Kushiro.
As an "equipment" follow-up to my recently uploaded Solo Touring in Eastern Hokkaido entry, I’d like to introduce in more detail what I brought along. (I went through all the trouble to go, so I’m going to make the most of it!)
OUTER SHELL / TADE QUI Bags
The three types of OUTER SHELL bags and the TADE QUI bag were incredibly useful.

The gear was based on the assumption of 3 days and 2 nights without doing laundry, staying at hotels/inns, and using a laundromat every two days. Here is everything I brought. (I lost my wind shell while on the trip...)

TADE QUI: Cunningham Camera Bag

I kept things I wanted to access quickly in here: my camera, power bank, wallet, sunglasses (or glasses), aid kit, and keys.
I chose the TADE QUI handlebar bag because the flap is secured not with a bungee cord, but with a non-stretchy tactical cord.

Since I was using a PEAK DESIGN mount on the stem for my phone to use as a navigation tool, I didn't plan on opening or closing the bag while riding. I wanted something that was firmly fixed and wouldn't sway. Another reason for my selection was that the interior is designed for cameras (the product concept itself is a front camera bag), meaning there was no need to add extra inserts.

OUTER SHELL: Stem Caddy

I mostly kept this empty and used it to store snacks I picked up along the way.
The design allows you to open and close the bag with one hand, which is very well thought out, and personally, I find the square, angular shape to be cool. In my daily life, I keep an ABUS chain lock in there permanently so I never forget my key.
OUTER SHELL: Half Framebag

I kept items needed for repairs or relaxing breaks in here: spare tube, spare rim tape, multi-tool, portable pump, zip ties, and as a smoker, my cigarettes and portable ashtray.
While this frame bag has a small capacity, it doesn't block the bottle cages, making it the first choice for a trip in summer where carrying two bottles of water is a must.
If you use a dropper bottle cage, you can fit a double-walled stainless bottle, allowing you to enjoy cold water along the way. (For reference, my frame size is TT51, and I chose size S.)

Coming from hardcore bike packer Kyle, the shape is clearly well thought out.
OUTER SHELL: Dropper SeatBag

I kept items here that I wouldn't need access to while riding: my bike travel bag (rinko-bukuro), change of clothes, socks, toiletry kit, a sacoche for moving around after the ride, bath set, rain jacket, gloves, and batteries.
Furthermore, I externally attached my BEDROCK SANDALS, a speaker, a pouch containing sunscreen and ointments, and a bear bell.
(When it comes to external storage, it helps to think in terms of "I need this accessible externally," rather than "I'm attaching this because it won't fit inside.")
Voile Straps were essential for this external attachment.

Even if you don't have a specific use in mind, Voile straps are useful for all sorts of things if you bring them. (They are incredibly helpful on the road—for securing tires when traveling by train, increasing external storage capacity, or strapping on layers you've removed. You really can't go wrong bringing three 20-inch and one 32-inch Voile straps.)
Ideas just keep flowing while I'm riding.
Definitely bring these on your trips!
Items I was glad I brought
PEAK DESIGN Out Front Bike Mount

Currently the best device mount for keeping your smartphone on the cockpit to check maps, send messages, or perform searches while traveling.
No issues even on gravel; it has a rock-solid, non-slip grip. Yet, it detaches with a single touch, which is a brilliant feature.
The fact that you don't need to twist or perform awkward maneuvers to detach it shows how well-designed it is.
An essential for solo travel.
USB Charger with Built-in Battery
A charger with a built-in AC plug.
You can charge it at your accommodation and use it as a power bank on the go, which reduces the total amount of gear you carry.
Personally, I recommend this one from Anker.

If you consolidate your charging cables to USB-C or USB-A, it’s convenient to have the minimum number of cables.
It gives me peace of mind as it can fully charge an iPhone 14 twice while in power bank mode, and you can charge your devices even while the charger itself is plugged into a wall outlet.
Zip Ties

It's best if you don't have to use them, but they are useful for emergencies like breakage or losing a bolt. Having something to perform a quick, temporary fix is invaluable.
Rubber bands are another useful, humble item to have.
Sunscreen
Essential, because a bad sunburn that feels like a minor burn will drain your energy. Choose one that is sweat-resistant. When it comes to things like this, I personally pay attention to the fact that they should be easily available anywhere in the country.
Different products have very different scents that can make me feel nauseous, so it's best to use one you are accustomed to.
After trying many, I’m currently using this one. It has no scent and is a great value.

I’m still researching, so please let me know if you have any recommendations.
RAL Pack It Right

Essential for the reasons I wrote above. (I'm the type who says important things twice.)
You definitely won't go wrong bringing three 20-inch and one 32-inch straps.
Ziplock Bags

Useful for items you don't want to get wet (electronics), or items that are wet and need to be separated (bath set, clothes caught in the rain). They are also great for things that would be a pain if they got scattered.
Carrying about two bags is useful for all sorts of situations.
Camera

I always carry a camera for report purposes, but for this trip, I used a Leica M-P (Type 240)—a model released in 2014 that I had the chance to purchase last year.

Since it's a full-manual camera, I generally can't shoot while riding, but since this trip was about stopping and taking my time in good scenery, it wasn't an issue. Plus, shooting while riding is dangerous anyway.
The reason I took this camera on the trip was its "battery life." If fully charged, it lasts for about 10 days even if I take 100 shots a day. Apparently, this is a feature of the Type 240 among digital Leicas.
In other words, you can reduce the amount of gear like chargers and spare batteries.
I was a little nervous so I brought the charger, but the trip ended without me having to charge it even once. I can probably go even lighter next time.
Not just for cameras, it's always good when digital devices have long battery life.
Avoid carrying things on your back
Personally, something quite important when touring is to "avoid carrying things on your back as much as possible."
I like to leave the luggage to the bike as much as I can, keeping myself light.
Just doing that gives you more peace of mind and allows you to ride while feeling the terrain of the land in a relaxed way.
There are other styles of touring, like camping, but I went on this trip with this type of gear.
I want to go to even more places and see scenery I've never seen before.
Circles will be closed for the Obon holidays until 8/25 (Fri), but it seems the staff members are headed to all sorts of places, so I’m looking forward to the reports on what styles they used!