I'm inclined to think that Akira is dead, I mean why else would the Host Samurai know that Kurono was Akira's brother, they probably found out that he leaked information to Kurono, they questioned him and killed him later.
Although it is a little strange to think that Host Samurai would carry a head on his hand all the way to Kurono's home.
When I saw Akira in the manga, I thought that somehow he will succed among vampires and there would be an amazing brother vs. brother battle. Finding Akira to be killed too soon really dissapointed me... But if he is really death, his revival possibilities are almost null.