The first way is to make it yourself using Vroid Studio! This is the most common way, and you can find a lot of materials by Googling or watching YouTube tutorials.
If you have limitations with your design, you can get various parts such as hair, eyes, and clothes through the Booth.
Or you can download VRM files from the websites below.
You can get VRM and PMX (used in MMD) files from the site below.
Please be aware of the copyright of each file you use, and I am not responsible for any problems that may arise from this.
PMX or FBX files can be converted to VRM through specific tasks.
I wrote a guide to converting to VRM model using this. Give it a try!
I will write a detailed guide for the game in the same format later. I would appreciate any feedback on the guide. There are other ways, but I think this is probably the most free from terms and conditions and uses the lightest programs.
I'm working tirelessly to complete the function. Good luck, and I hope my game will be lucky too. Thank you!