Episodes include only the fully completed content from the game, divided into chapters (4 of the 5 existing chapters are available for purchase). The advantage is that in order to unlock all scenes in all episodes, you do not have to replay the game each time, there is a "fast way" for each scene in each episode.
However, the episodes available for purchase do not include all the new content that is only available in early access, such as bonus scenes for Patrons or Episode 5, which is in development.
The difference between episodes and the demo client on this page is that the demo client does not include the ability to skip text and multiple saves of the game.
If you want to enjoy the FULL game with all the scenes from early access - subscribe to our Patreon: patreon.com/titdang