The relationship could develop through shared secrets. Aiura already has her own powers and secrets. When she realizes that Saiki has much bigger secrets regarding his psychic powers, she might become his confidante. They would bond over the need to keep their powers hidden from the world, and this shared burden would bring them closer together in a deep and meaningful way.
One possible plotline could be that Aiura Mikoto discovers Saiki's psychic powers and tries to use her own powers of divination to help him control or better understand his abilities. For example, she might foresee a situation where his powers could cause a great disaster and they work together to prevent it.
The Saiki K manga ended. It wrapped up the storylines and gave a satisfying conclusion to the readers. Although it's over, it still holds a special place in the hearts of fans.