Ulquiorra's relationships (Roleplay characters may be added):
Kurosaki Ichigo:
Initially, he referred to Ichigo as "trash" and considered him unworthy
of being killed, mostly because he believed that his unstable spiritual
pressure would eventually destroy him in the long run. The first time
they fought in Hueco Mundo, Ulquiorra was able to provoke and in turn,
defeat him at full power without even unsheathing his blade; he also
impaled Ichigo's chest with his hand, leaving a hole resembling his own
Hollow hole. Grimmjow stated he only does this to prey he finds
particularly interesting. In their second fight, Ulquiorra acknowledged
Ichigo as an opponent worthy of killing, finally unsheathing his blade.
Later, when Yammy interrupts their fight, Ulquiorra repeatedly reminds
Ichigo that if he wants to fight anybody else, he would have to kill him
first. Presumably, Ulquiorra's ulterior motive was to draw out Ichigo's
full potential, but this seems to have backfired on him.
Inoue Orihime:
He was placed in charge of abducting Orihime, and subsequently, taking
care of her well-being until she was needed by Aizen for her powers. His
relationship with her appears to be limited to the task of bringing her
food and occasionally informing her of her friends' struggles
throughout Las Noches. He refers to Orihime as "woman" (onna;
"girl" in the English Dub), both in thought and conversation. It can be
noted that Ulquiorra seems rather intrigued by the concept of the 'human
heart', questioning her about how she is so easily able to wear her
emotions on her sleeve. During their most recent fight, Ichigo mentions
Ulquiorra may have "become more human". This could signify Orihime's
empathic personality affecting Ulquiorra's own emotional capacity. This
is further highlighted when, at the brink of death, he reaches out to
Orihime and asks her if she's afraid of him. She responds in the
negative, and reaches out to touch his hand just before he disintegrates
into dust. Through his bond with Orihime, Ulquiorra finally realizes
what a heart is; even refuse his earlier materialistic arguments by
remarking that he has it in his hand.
Yammy Llargo:
He treats Yammy as an inferior and seems to have the weaker Espada's
respect. Because of this, their relationship seems to resemble that of
an Espada and his Fracción. This is evident throughout their various
conversations, which often consist of Ulquiorra ridiculing Yammy. At one
point, Ulquiorra even resorted to using violence to get Yammy's
attention. During Ulquiorra's second fight with Ichigo, Yammy attempts
to help him, although Ulquiorra coldly refuses. He is stunned and
disappointed when Ulquiorra dies, though more from surprise that he was
beaten and annoyance that he didn't get to help in the fight rather than
concern. Ironically, Yammy later tells Ichigo that Ulquiorra, along
with the other Espada Ichigo had fought, were "trash" compared to his
own released form.
Aizen Sõsuke:
He is quite loyal and obedient to Aizen, fulfilling all of his orders
without question. However, it can be noted that he has occasionally been
seen disobeying Aizen's orders in favor of his own, personal
curiosities, such as when he purposely sought out Orihime Inoue to
question her about human emotions.
Grimmjow Jaegerjaquez:
It would appear that he is not on good terms with Grimmjow, having
challenged Grimmjow's ideals several times. Ulquiorra makes small
observations to insult Grimmjow some of which fly past Grimmjow.
Grimmjow believes that he is stronger than Ulquiorra and is eager to
prove this. He and Grimmjow have conflicting personalities, the probable
cause of their bad relationship.