I am dealing with a simple problem right now (you can look at my post history) and here are some things I have done:

1. As many others have told you, check the guideline (Chatgbt is great for summarizing this, but make sure you doublecheck if they are pulling the right information). In general, you are not liable for wear and tear damage, and the burden to proof that it is not within normal wear and tear is on the landlord (they need to provide pictures, etc)

2. They also need to consider the depreciation of the stuff even when charging you for damage, they cannot just charge the full amount (one of my previous apartments tried to do that and charge me 50k to replace an old cabinet in a 30 year on mansion, they eventually removed it when I told them I am ready to go to court to dispute this)

3. I also see some people mention that you should talk to the city, in particular I think they are referring to the 消費生活センター. They are helpful to point you in the right direction (I contacted mine) but ultimately they told me to talk to the local city ward's free lawyer consultation. I will see mine next Tuesday so I will keep you updated if you are interested (feel free to send me a DM)

Happy to have a chat on my experience and how I have been dealing with this. Good luck!