Can I Only Be a Supporting Character in Every World?

I, created by the System, am required to go to worlds where the original plot has gone off course, find out why, and fix things?

And so I don't make the plot fall apart even more, I can only take the place of someone who originally lived in that world?

And since most of the plots are connected to the protagonist, I can only take the place of a supporting character?

Currently in: The Garden of Sinners

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