You can tell much more than surface burns by her features, age, personal accounts of history, and her manner of speech.
As a small example
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. The only symptoms of which explain Sylvie's hair and eye color.
Maybe I've simply looked too much into it, but Sylvie isn't really an example of anime or video game logic.
The game has a whole new level when you consider Sylvie's physiological an psychological condition beyond "she has scars".
You might have breezed past the opening, but you apparently missed out on the main draw of the early game.
Probably only cared about it for the porn and jumped straight into remorselessly having sex with her too.
Sylvie and her little game are perfect if you have an interest in the medical field.
An experience spoiled if you've played the game for months or years without considering that angle.