Colonial and oppressive cultures often hyper-sexualized the people they oppressed as a way of showing that their supremacy was necessary in order to bring moral guidance to the indigenous peoples. It makes me incredibly uncomfortable to read this manga because of how the native people's are represented. If you look at how most indigenous tribes in snowy, Northern climates dressed, you're not going to see a history of walking around topless outdoors.
In addition, having these native people represented with no complexity around their happiness to serve is another layer of cringeworthy.