Noriko Mitose isn't strangely credited but it's her that sing "The Personalizer", look here
http://www.youtube.com/watch?v=QZWmkXC-81g, maybe one of those 2 singer mentionned made a cover of that song, dunno, but there are no more informations about that, but if it only says "Brostep Edit", at least there's probably 99% of chance that it's still Noriko that sing that song.
About others one "ใกใใ" is Chiyoko for sure the Chiyoko from IOSYS because it's precised but for Himawari Natsuno, can't tell because it says only "Himawari" but website doesn't mention Hatsuno.