I'm less than 2 weeks away from my 1st time trip to Japan. I am going solo and I wouldn't have been nearly as prepared if it wasn't for this Reddit. So, thank you. This is what I've got!:

Day 1: Fly into Haneda then 4 hours later fly from there to Tokushima. Rent Car. Go to the hotel's hot spring. Sleep
Day 2: More hot spring. More sleep. Temple 1 of the Shikoku Pilgrimage. Ropeway. Awa Odori. Maybe Hyotanjima Tour Boat
Day 3: Drive to Iya Valley. Sightseeing. Zip Line over the Oboke gorge. White Water Rafting. Hotel Onsen
Day 4: Ryugado Caves. Nakatsu Gorge hike. Canyoning Niyodo River
Day 5: Canyoning again! Down a waterfall this time. Possibly drive to Mount Ishizuchi (if so, probably just take the ropeway and come back down). Then drive to Imabari to drop off car and sleep
Day 6: Mail luggage to Osaka. Ride half way through the Shimanami Kaido. Take a bus or a boat to Onomichi, then a train to Osaka
Day 7: Rainbow Festa! explore
Day 8: Universal Studios (mainly for HHN and the Demon Slayer stuff)
Day 9: Train to Kyoto. Philosophers Path
Day 10: Arashiyama for Bamboo Forest rickshaw, Monkey park, kimono forest
Day 11: Back to Arashiyama for Sagano Scenic Railway and boat ride. Owl/Bengal Cat Cafe. Something for Halloween
Day 12: Gion Odori
Day 13: Train to Hakone. Hotsprings
Day 14: Feudal Lords Parade, ropeway, Open Air Museum, Fukazawa zeniorai benzaiten shrine (bring coins), .Romance car (2nd row :) ) to Tokyo
Day 15: Samurai restaurant. Akihabara
Day 16: DisneySea
Day 17: Art gallery. Ninja restaurant. Ping Pong tournament. Joypolis.
Day 18: Shopping. Animal cafes. Maybe car mee/drive.
Day 19: Back home (sadly). Unless the Orange man wins the election and then I'm staying.

Some days are packed. Some I have time to play it by ear. I'm still revising.
i've only got 4 places I know where I want to eat. All else I'll find where to eat as I go along.

Some things I won't get to do that I wanted to do: Ōkunoshima Bunny Island. tomogashima. More temples in Shikoku. South Shikoku. Ioki cave. Koyasan Okunoin. Fuji-Q Highland.  Izu Islands. Sumo tournament. A bunch of stuff North of Tokyo. Sunflower Murasaki ferry

I signed up for a mobile Suica card on my phone. It was easy with google translate.

You read all this? Thanks :)
Any feedback is welcome.