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 more option is to ask in anime - related forums. There are many forums where anime fans gather to discuss different shows. Post a question asking for good 'saiki kusuo fanfiction' and you're likely to get some great suggestions. Also, keep an eye on the official 'saiki kusuo' websites or social media pages. Sometimes they might feature or recommend some fan - made works including fanfictions.
Nendo could be a great addition. His simple - minded yet loyal nature can add some humor and unexpected twists. For example, he might accidentally almost expose Saiki's powers while trying to be helpful in a situation involving Teruhashi.