Bio blurb on them here:
http://www.junglewalk.co.jp/369/staff.html. No terribly interesting info about them, except when they formed (2003) and where they graduated (Matsumoto: Tokyo College of Music, Yu: Tokyo University of the Arts).
Based on web mentions and
other profiles, it seems like they're mysterious because they're not especially prolific: arrangement/orchestration/performance credits on songs here and there with the occasional score.
Here are some other works beyond the scope of VGMdb: