Agatsuma Soubi (我妻草灯)
Twenty years old, and quite an enigma. He was Seimei's fighter as Beloved, and despite still bearing that bloody marking on his neck, he now fights under the Loveless name with Ritsuka. His birthday is September 28, his bloodtype is A, and as Kouga Yun herself described it, he has "tea" coloured hair.
He is forceful with most people, yet still a lapdog to others. He treats those who still have their ears with disrespect, but he regards Ritsuka and Seimei with reverence. He claims to dislike pain, yet he encourages Ritsuka to pierce his ears and punish him. He says he doesn't want to be pushed around, but he craves orders. If you judge him just by the first few volumes, he just comes off as a pervert (or maybe just a masochist), but the more his childhood is delved into via flashback the more it is apparent he is just a very damaged man grasping at straws for guidance and any form of love. At a very young age, he lost his parents and was taken in by Ritsu, a man who hated him and yet still had an obsessive fascination with his looks and a selfish interest in his future as a fighter. Ritsu trained him to be the very best, and doesn't appear to have ever been gentle with his trainee, even resorting to whipping to make Soubi accustomed to pain. Although it is not stated plainly, all signs point to Ritsu as for who took his ears, and it apparently happened when Soubi was not much older than Ritsuka, judging from the flashback chapter in which Nagisa reacts to the newly earless Soubi. Later, that same father/disciplinarian figure handed him over to a sacrifice who wanted nothing from him but unquestioning loyalty. Their career (so to speak) together is mostly untouched material in canon, but the brief glimpses show a cold, harsh relationship. Why Seimei tossed him aside is unanswered, but it's clear Soubi took it hard.
The effects of his messed-up youth are the primary source for his strange personality and actions in the present, particularly in his interactions with Ritsuka. Though Soubi is very secretive and doesn't reveal much about himself, they complement each other and whether Soubi fully realizes it or not, he is repeating some of the same things Ritsu did, if in a kinder, gentler way.