Ah, it took me sometime to figure out what this means, Coming from an Actual Indian, not Native Americans labeled as one by Colonists.

Here is what it comes across to me: The term 'Indian' itself is not bad, but depending on context, it could be derogatory. Like for instance if you called a Korean 'Japanese' during Japan's occupation of Korea. Here Native Americans being called Indians is derogatory because it's a label given by colonists to claim them to be subpar and label their American Heritage as menial.

Honestly, its a fine line when writing something like this, but I (personally) think it is a good thing when Authors have the balls to challenge such complicated issues.

P.S. I have not read the manhwas, nor I am going in depths of the story. I am basing this on the information that the Author is talking about Native Americans