Rikka Takanashi - Shinka is friendly towards Rikka despite being irritated at times with Rikka's delusions. She also helps out Rikka in situations regarding Rikka's romantic relations with Yuuta.
Yuuta Togashi - Shinka initially hid her true colors from Yuuta, whilst Yuuta initially admired Shinka. She dated Yuuta once, but breaks up with her after he lost his admiration for Shinka upon learning of Shinka's true behavior and her chūnibyō past as Mori Summer. Even then, they still get along, and Shinka would help him to improve his romantic relationship with Rikka.
Sanae Dekomori - Shinka and Sanae have a troublesome, often hostile, relationship. Sanae admires "Mori Summer" a lot but doesn't believe that Shinka is the real one, thus calling her "Fake Mori Summer". Later, Kumin reveals that she thinks that Sanae actually wants Shinka to be the real Mori Summer. Despite Shinka and Sanae's relationship being so troublesome, Shinka still values her and all her friends and wants the best for her.
Satone Shichimiya - Satone and Shinka had known each other in middle school. Sanae took part in Mori Summer's ceremonies with her. They were partners too, and Satone used to admire her a lot. Satone and Shinka are still good friends, although Shinka lost her chuunibyou self while Satone still keeps hers.
Makoto Isshiki - Isshiki was one of those boys who admired Shinka because of her beauty and politeness. He rated her as "Most Beautiful Girl" in a beauty poll of the girls in their class. After finding out her real personality, though, he lost his admiration for her just like Yuuta.
Kumin Tsuyuri - Shinka gets annoyed at Kumin because of her air-headed personality a lot, and often hits her. But they still have a friendly relationship, and Shinka loves her as a friend, along with the others.