Its 12 episodes long.
Its about the main charrie Ristuka.His brother Seimei aka Beloved was burned to death two years ago by an organization known as the Seven Moons. Ristuka is a sixth grader who transfers to a new school.At first everyone thinks he cool and cute.But then they start to see him as being rude so they stop liking him. Later he meets Soubi, who claims to have been Seimei's friend.Ristuka, wanting to know everything about his brother, decides to get to know Soubi more.He finds out Soubi was actually Seimei's "Fighter" and Seimei was Soubi's "Sacrifice". The battles in Loveless are based on the teams of Fighters and Sacrificers. Each share the same "real" name,Soubi and Seimei's was Beloved and Ristuka learns his name is Loveless. The throughout the series Ritsuka is searching for information about the Seven Moon's and who exactly killed Seimei, while battling other fighting teams and becoming closer to Soubi.
Everyone is born with ears and a tail, but when they lose their virginity they lose their ears and tail. So people are leary of others without ears, such as Soubi.
and yes, this is a Shounen-ai series, with parts being Shoujo-ai.
Well theres my attempt at explaining the world of Loveless!