His name, Himura Youichi, was never revealed in the Manga and first mentioned in the second season of the Anime. He once went to Minato to ask for help in order to escape the city. Minato however refuses and soon after he got nearly killed by Karasuba. Later in the Manga he is mentioned again, he apparently took out Mimi, a Sekirei of Mutou in the second stage of the Sekirei Plan.
Himura is a tall, relatively slim build brown-haired man who wears spectacles, a black jacket with a red shirt underneath.
He looks down on the Sekirei he has defeated in the first stage, even going as far as calling them small fry and weaklings. But once it gets tough for him he tries to run away. Kunimitsu Hiroyuki described him as creepy and thus didn't trust him when Himura approached him to take part in his escape attempt.