At first, Teruhashi didn't know much about Saiki. When she crossed him in the road, she mentally made fun of him, and said that it was sad how he didn't have any friends. She then claimed that she felt sorry for him, approached him, attempting to start a conversation. She goes up to him and greets him, thinking about how he must've fallen in love with him already. To her surprise, he instead bows and walks away, shocking Teruhashi. She then thinks about how he must've been so nervous that he couldn't speak to her. She then starts making assumptions, and continues to bother him.
Then, he calls her troublesome and thinks about how she's spending her summer is sad too. Teruhashi believes that Saiki thinks she is but an illusion, which makes him a little grateful to the situation. They then cross Nendo, and Saiki thinks that it's bad, as he would have to acknowledge her when he notices them. Saiki attempts to go past him with success and takes the moment to teleport somewhere else, where Teruhashi doesn't see him. Teruhashi then realizes that she actually likes him, shocking Saiki.
Still, Teruhashi remains unaware that he knows about her crush. One day, Saiki's class goes on a field trip, where the groups are drawn by lots. There, Teruhashi asks the gods to get Saiki's group, which is the paper she reaches for, until Saiki switches the papers up and she ends up with Takahashi. Teruhashi is still able to get into Saiki's group. When artiving there, Saiki takes a nap, where Teruhashi sees him. She takes off one of his control devices, sending her to another island. When waking up, Saiki is worried for her safety and checks if she's alright. When seeing that she isn't injured, Saiki is relieved but it fades away when he sees that there is a bear in front of her. He then teleports to her and punches the bear away, where Teruhashi thinks that she is dreaming and starts clinging onto his arm. She then wishes to be in a castle, which Saiki does. Then, she asks him to say "offu", which he is reluctant to do. He then uses Toritsuka to grant her wish, and takes her back to the hotel.
When Saiki tries to get Akechi back after he's turned to stone, Saiki turns up in another universe. There, the two are dating and act like a couple.
In chapter 242 of the manga (episode 24, season 2 of the anime), Teruhashi overexerts herself by staying up for several nights to memorise everything about her male classmates in an effort to make them happy while also maintaining her reputation. Saiki notices her efforts and commends her for being so perceptive and hard-working, saying that she "can read people like a psychic". However, due to her exhaustion, she passes out, and Saiki catches her. He is shown to be angry at their classmates saying "None of you noticed. Teruhashi-san noticed all kinds of things about you all, but not a single one of you noticed how exhausted she was". The boys seem to be more concerned about Saiki being close to Teruhashi rather than her actual wellbeing, seen by how they tell Saiki to "get off her", creating an obvious difference between Saiki's relationship with her and the others' rather shallow obsession with her. Saiki carries her to the nurse's office, and upon waking, the boys tell her that Saiki "showed up out of nowhere" and caught her. Teruhashi is shown to be touched, and ignores the boys to go and thank Saiki.
Due to its simplicity and the most attention from the authors, SaiTeru is the very first and most famous ship in the franchise. In particular, it was Teruhashi's crush for Saiki and her rivalry with other girls that were devoted to the ending animation of the anime adaptations. Either way, Teruhashi appears so frequently in the manga and anime as the character in charge of the romantic subplot that many fans of the ship mistakenly confuse her status as main love interest with Saiki's canon partner. In this regard, the fact that the franchise ended at a seemingly open end in terms of romance was found "disappointing" by many of them.
On the other hand, due to the controversial attitude towards Teruhashi among work's fans, as well as the obvious popularity of slash shipping for the shonen franchise, this ship has many rivals, for example, Saiai, ImuTeru and KaiSai.
It is currently the third most popular ship on AO3 and the most popular on Pixiv among the fandom with 900+ works.
|SHIPS||het||AiTsuka • SaiTeru • Saiai • YumeKai|
|slash||KuboKai • KaiSai|
|femslash||ChiyoMiko • ImuTeru • TeruAi|
|poly||PK Psychic Trio|