Those chapters are a sequel to Miserarete, which is Akira's brother's Kaoru's story. I don't believe Daichi has a brother that we've seen. Hitomi No Giwaku is the sequel to this.
Miserate is actually a prequel to this, the last chapter is of Akira at 23y old. http://www.mangago.me/read-manga/miserarete/

fucked up shit ^^ he is really a psych. and who are all these other persons at the end of the 2 last chapters? suddenly daichi has a brother. and all black haired guys look nearly the same. it was to hard for me and all in all I didn't like it much ^^