|Also known as:||Beloved, Sei-san|
|Manga:||Chapter 1 (flashback)|
|Birthdate:||November 14, 1985|
|Family:||Aoyagi Ritsuka (brother)|
Aoyagi Misaki (mother)
|Battle:||Agatsuma Soubi (previous sentouki)|
Akame Nisei (true sentouki)
Seimei Aoyagi (青柳清明 Aoyagi Seimei) is the older brother of Ritsuka Aoyagi. He was born on the 14th of November, and his name comes from the lunar day “Seimei”. When he was seventeen, he was found murdered in Ritsuka’s classroom at school, although he could only be identified by his dental records as he had been set on fire. Later in the series we learn Seimei faked his death, but the person who died in his place has not been revealed.
Seimei is the Sacrifice of the Beloved pair. At Seimei’s request, Soubi Agatsuma(Seimei's Fighter) was given to Seimei as a Fighter when Seimei was only fourteen years old, Soubi being seventeen at the time. Fans of the series have speculated that there is a rivalry present between Seimei and Ritsu regarding Soubi, but nothing in the manga confirms these speculations.When Ritsuka lost his memories, Seimei became an extremely important figure in his life, protecting him from their abusive mother Misaki Aoyagi and being a great source of comfort and trust. Because of this, Ritsuka was hit hardest of all by the news of his brother’s death, and is very bitter and vengeful towards those who may have been involved in his murder.
His personality is subject of great debate and many readers have differing interpretations of his actions. This is made even more confusing by the clashing beliefs of the different characters in Loveless. Ritsuka claims Seimei was kind, gentle, loving and protecting, and their mother believes Seimei will stop her from hurting Ritsuka. Soubi, however, is almost afraid and spiteful of Seimei, and others such as Nagisa and 7 think of him as cruel, merciless and hateful. They state Seimei always acted strangely, close to no one and refusing to even eat in front of others. Kio Kaidou harbors an extreme hatred for Seimei over how his friend Soubi was treated, although Soubi refuses to confirm whether there is truth in Kio’s accusations. Ritsuka denies all this, though has some startling flashbacks which show a more disturbed, obsessive side of Seimei, even showing behavior that was borderline incestuous towards Ritsuka.
Seimei has said in volume 7 that in his world, he and Ritsuka are the only humans, and that everyone else is an animal to him, going on to state in volume 8 that Ritsuka is the only human alive that is exactly like him. When he meets Ritsuka again he questions whether Ritsuka would still love him and give himself to Seimei completely, body, soul, love and mind.
However in volume 8 is was confirmed that Seimei does indeed have a violent personality or destructive tendencies – he gouge Ritsu's eyes after a brief, heated conversation about Soubi and uses the man’s blood to write the haunting message “Ritsuka, I’m back” on the wall. Ritsu is left blind by this attack. There are suggestions in canon that Seimei possesses powers beyond that of a normal Sacrifice and has been described by Soubi and others as inhuman.
In Volume 11, Mikado describes Seimei as incredibly smelly.