Yuki & Hanabusa

Yuki Cross (Kuran) and Hanabusa Aido have some moments in the Anime, mostly comical ones. At first, Hanabusa treated Yuki in a disrespectable manner, calling her by saying "Hey You!". As the series continues, Hanabusa begins to refer to Yuki as "Cross Yuki". Later on, when Yuki is revealed to be Kaname's younger sister and a pureblood, Hanabusa begins to respect her more. Part of him does the respecting towards Yuki for Kaname, but the other part was because Yuuki was a pureblood, and a princess too. From the discovery of Yuki's past, Hanabusa began calling her "Yuki-sama" and occasionally adding "Cross Yuki" by mistake, then correcting himself. Hanabusa also noted that "Yuki's personality changed when she became a vampire".

It also appears that Aidou might possibly have romantic feelings for Yuki, in one of the early chapters, he asks the Day class boys if they think Yuki is pretty, they answer with yes and Aidou agrees.

After the one year time skip, Aidou is seen as her teacher. 

Aidou tries to follow Yuki in purpose of trying to protect her when Kaname is not there. Though he tries his best, Aidou fails on keeping Yuki at the Kuran mansion and usually is convinced by Yuki to let her have exceptions to go outside into the nearby town (as shown in chapter 57 of the manga).