Hey, can I ask what program do you use to make this game? I'm relly intrested. Best game in here by the way.
What do you mean exactly? The game engine should be Ren'Py. But I don't know what the developer uses for rendering and animation. Are you just interested or do you want to make a game like this yourself? But I warn you, if you're really going to make a game like this yourself, I should say this is a fucking much work, not just programming. You have to make pictures, animations, character design, you have to write an interesting story. You need unique characters with their own personality and feelings. It's not like I want to say that you shouldn't be doing this game. You should only know how much work and time it takes to make such games.
You can try Ren'Py for a little game but big games just need much more time and knowledge so it is possible but hard as a one man project and you need good software and hardware for animations and pictures. I dont want to say you should not try to do a big game I just want to say dont try to make a big game as first try with Ren'Py. Just make a little game with one or two Characters and a short story.