Out of all the inner-circle students of Class F, Aiko seems to spend the most time with, and devote most of her attention to Kouta. She often teases him, due to his perverted nature, and causes him to get deadly nosebleeds. The two also seem to have a possible rivalry in the Health and Physical Education subject, due to their high scores. It is implied that Aiko likes Kouta, and that her teasing is an attempt to gain his attention while messing with him at the same time.
She even pesters him with tease-worthy lines to get him to notice her swimsuit.  She also states that she'll join him as his partner during the Test of Courage incredibly fast. Both of them have skills with technology, including the micro-recorder.