Artist's commentary
Her body contained a deadly toxin developed in order to wipe out all intelligent life on Erden, and she was created with the sole purpose of delivering it to its target. Her beauty was supposed to captivate as many human men as possible, and they in turn were supposed to become the next carriers of the toxin. However, the plan failed. Kaguya didn't want anyone on Erden to get hurt, so she decided to prevent that by avoiding human contact altogether.