I have been doing research into what engine I want to do my VisualNovel in, and I prefer Monogatari since it has SVG support. To do what I am needing for characters/items/backgrounds I would like to use Rive to have smooth vector animations.

https://rive.app/

Rive used to be two applications of Flare (vector animations) and Nima (raster animations) both have been combined into one app of Rive. The editor is a website that can be used for free, and the runtime is open source: https://rive.app/runtimes or https://docs.rive.app/runtimes/links-to-the-flare-runtimes of the different runtimes I figured you would be needing the JS version.

I have not tried myself yet at using this with Monogatari, but figured I would mention it here since yall are working on the next major version. When I get the chance ill try using Rive, but am still getting used to it. I do not think it has an android version yet, but it is in their roadmap. It does seem to have an iOS version though.

Thanks