The full name of a2c is most probably Atsushi Yokoyama, as shown on the following scan from the album "first odyssey of fripSide":
http://www.bigblah.net/upload/1stodyssey.jpg
Atsushi "a2c" Yokoyama is credited as the guitarist on track 6, which was remixed by the group "azure". To make doubly sure I went to their
profile page, and sure enough a2c of MintJam is listed there as a support member.