It looked to me like Shu-chan was Narita's college friend first. With the bar chapter being Narita introducing Shu to Aya, telling the story of how Narita and Aya met in high school, and how Aya is when she drinks. So this might just be a case of Shu still getting to know Aya and being uncomfortable with her general Aya-ness. Their energies are totally different. 
Also whenever people are constantly talking about someone you don't know like Narita and Aya do with Koga it can feel excluding. I think if Koga hung out with them too vibes would be better, but she isn't a fellow student obv. 
last edited at Nov  2, 2025  7:01PM