Since someone is having trouble opening the gallery, I made a "little" guide on how to open everything and get some endings. I hope the author of the game does not mind.
You can simply view the map with the extension (mindmup 2.0 for google drive). Download this file to google drive, install the extension and open the map, everything is simple.
https://drive.google.com/file/d/13g3IrxfkbFdUgCzQfJJheAs95We0J-bs/view?usp=shari...
It's essentially a skeleton of the game with choices that allow you to unlock arts for each route.