After watching the Light Music Club's performance during the freshman reception , Azusa thought of Yui as a very talented guitarist, eventually this thought led her to join the club. Soon, however, she regretted thinking highly of Yui and now thinks of her as a student who just likes to procrastinate.

Azusa admires Yui due to her certain abilities, such as her ability to go far due to sheer determination, her perfect pitch, and her affection towards her friends. Despite being better at guitar than Yui, she insists that Yui played the lead guitar due to her seniority (though in some songs, usually opening songs, Azusa plays the lead guitar instead). Before Azusa's first concert, Yui was sick and unlikely to be able to play. Azusa was the one who brought up the idea to cancel the concert, since it would not be good for anything if the whole band would not be present in her eyes. When Yui actually showed up, Mio told her to apologize to Azusa since she was the one who worried the most about her.

Yui had become attached to Azusa immediately, often hugging her, and gave Azusa the nickname "Azu-nyan" (-nyan is a Japanese suffix associated with cats) after convincing her to try on a pair of cat ears and say "nyan", which would continue to be used by Yui throughout the series. Azusa would initially be annoyed by Yui's clingy behavior but grow accustomed to it and her nickname over tiime. However, when Yui crosses the line, (by trying to kiss her for example), Azusa will not hold back using violence to stop her, like slapping her face before the school concert or elbowing her in the stomach (when she mistakenly thought Yui was about to kiss her instead of her guitar).

Yui's laid-back personality does not usually work well with Azusa's more diligent character, but they have become quite close and managed to cooperate at times, like when they performed in a local talent show for Yui's neighbor. Overall, despite trying to hide it through her strictness, Azusa is fond of Yui and they become very close, even rooming together during the band's trip to London .