Since I haven't read it, I can't say for sure. It could be an original character created for this fanfiction related to the idea of clockwork and the concept of time running out. Or it might be characters from an existing series that the author has incorporated into this story with a new twist based on the 'time is up' theme.
We don't really know the main characters just from the title. But we can make some assumptions. Maybe there's a hero - like character who has been living in a world that functions like clockwork and now discovers that their time is up in a certain sense, like they are about to lose their powers or be removed from their position. And there could be an antagonist who is either causing this 'time is up' situation or taking advantage of it.
There's no way to know the main characters without reading the fanfiction. However, if we consider the title, it might involve a character who is somehow in control of the 'clockwork' system and another character whose time is up. For example, a time - keeper type of character and a character who has broken the rules of the 'clockwork' world and now faces the consequences.