Aria is Blair's younger sister, who got hurt in an incident with Lecty. Blair loves Aria very much calling her precious younger sister and wants to take down Lecty for causing the incident that injured her sister.
Lecty is her cousin however, she does not like Lecty much, blaming her for injuring her sister years ago.
Eisenach is the ancestor of Blair and her family.
Kanata treats her as a student much like the other E601 members. She gradually comes to like him and even kisses him (Volume 4).