View source for Tomonori Sawada

http://sonic.sega.jp/SonicChannel/creators/023/002.html
実は、ゲームギア用の『ソニック・ザ・ヘッジホッグ2』にお手伝いでBGMを1曲作ったのがセガに入っての初仕事だったんですよ

This is proof from Sawada himself that he worked on Sonic 2 for Game Gear, which would thereby make him Dawasa (the syllables of his last name backwards).  If I'm reading the sentence correctly, he contributed 1 piece of BGM to the game.  If his role in Sonic Gems Collection is a sign as to what his involvement was, it is most likely that he composed Underground Zone.
:Sigh. this kind of information is (one reason) why I really want to [http://forums.sonicretro.org/index.php?showtopic=23687 see these things properly translated]. Do you know anyone who can help with that? - [[User:Andlabs|Andlabs]] 19:15, 24 March 2011 (CDT)
[04/13] This one's a piece of cake.

It basically says 'In fact, for the Game Gear title "Sonic the Hedgehog 2" I helped with 1 composition of BGM as my first job for Sega.'

Since Mitsuyoshi clearly arranged and vocalized one of his own works for Sonic Gems Collection, it would only seem natural for Sawada to return to this, his first composition.  Just compare these two:

http://www.youtube.com/watch?v=Y-aV6_NMBMM - Sky High (Part 1)
http://www.youtube.com/watch?v=FDOulvC1mvw - Sonic Goes UG Mix

The latter especially should also be proof that Sky Sanctuary Zone is also Sawada's composition.