Aura and Nyx

Aura and Nyx are two twin sisters, each with their own respective abilities. Aura, the light haired sister that is a master of Light and Ice magic. Nyx, the dark haired sister that is a master of Dark and Fire. Together they are basically yin and yang. They are inseparable, so they've stuck together for the entirety of their lives. They've learned through magic, that they could extend their lives, so they haven't aged for 400 years. As one night came along, they met with the MC. They learned that the MC is also of great power, and they are curious about the MC. Together, they choose the MC to be their lover for the rest of their lives.