Kou is Rin's treasured friend. Rin acts like a mother and an emotional support to Kou and is often seen listening to Kou's complaints.It is also hinted that Rin has a huge crush on Kou which Kou is painfully unaware of.
Ahagon, Umiko Edit
Shizuku is Rin's superior. She is very aware of Rin's feelings towards Kou. She likes the Rin/Kou tandem to the extent that she supports, teases and set the mood for the two.
Rin is the first person Aoba interacted when the latter started. Rin is often helping Aoba when the latter's confuse or in trouble.