Need help filling the two days between my stay in Tokyo and Osaka

So me and my girlfriend stay in Tokyo till july 22th and our original plan was to go to Miyazaki for 2 days, then head to Osaka on the 24th. After a few days we realized why we shouldn't plan routes for our trip while high and we canceled our stay in Miyazaki, however we can't cancel our stay in Osaka that we had also booked.

So she suggested to stay at Mt Fuji (Kawaguchiko) for the 2 days in between because going to Japan without seeing Fujisan is like going to NYC without seeing the Times Square imo. However upon checking hotel/airbnb prices (📈‼️) I redirect my energy to finding a place to stay NEAR Fuji from where we can do a day trip instead to Kawaguchiko.

Currently my idea for that is: Otsuki.

• It's 1h~ from Tokyo
• It's 35m~ from Kawaguchiko
• Hotel/Airbnb price are cheaper (Already found a suitable one)
• It has a direct JR line to Osaka, our next planned destination

How it'll go is something like:

22 july: Tokyo > Otsuki Have a chill evening relaxing from the trip

23 july: Otsuki > Kawaguchiko day trip Do our things like rent bikes around the lake, visit Chureito Pagoda, etc Return to Otsuki

24 july: Otsuki > Osaka

Now I feel like this isn't the best idea to be honest, but I'd love to hear some voices outside of my own head and hopefully stumble across something better. What do y'all think?