At 2:33 in this game's OP movie, it credits the soundtrack to Hideki Yamamoto.
https://youtu.be/NFxZg-e9Axs?t=153
Also, according to the credits in the booklet for TILDE GAME MUSIC COLLECTION VOL,6 TILDE ⇔ REIKA [TILDECD-07], Hideki Yamamoto composed "FLY" as well, not Keishi Yonao.
Here's the page in the booklet with the credits:
https://vgmdb.net/db/covers.php?do=view&cover=1864
Lastly, is there any particular reason we're using "Tohnosawa" instead of "Tounosawa" for the title?