Hi! The engine I chose unfortunately was "Visual Novel Maker". I chose it because it was advertised as the engine for those who didn't know how to program; actually this was a mistake and also the engine is really abandoned. I'm learning Unreal to do the rest of my projects in this engine.
What software have I used to create the illustrations? Before answering that question you have to know that these illustrations are mostly 3D renders with collage of photographs of the time recoloured in many cases. So I have mostly used: zbrush, 3D Maya with Vray, Character Creator, Unreal Engine 4 and 5, Clipstuido paint and Fotoskecher.
