Many of these games are easily made using the combo of Ren'py as the game engine with the renders created with KKS (Koikatsu Sunshine) and it's other component CharaStudio.
If you use KKS/CharaStudio, I recommend you use the Better Repack versions supplied and put together by ScrewThisNoise.
With my games being free and open-source, they can be used as learning devices for game development using Ren'py and KKS/CS at the moment.
FOSS (Free and Open-Source Software) is your friend here, it will cut the costs of software needed for game development.
LMMS for example is a DAW (https://itsfoss.com/lmms/)
Renpy is a game engine used for more than just simple VNs (https://www.renpy.org/)

