Excellion/Relationships

The Composer
The Composer is a very old friend of his, sharing his birth date and being the only other person whose existence was defined before the "big bang".

Sho Minamimoto
Excellion is Sho's mentor, and the only person Sho is completely loyal to.

Kosmos Lucis Caelum
Excellion's little sister, they haven't been seen interacting much aside from a couple of flashbacks.