Yoshiaki Kashima
From Sonic Retro
The worklist in the archived site here (http://web.archive.org/web/20020605053210/bn.sakura.ne.jp/~milpo/works.html) includes one key game: Seima Densetsu3X3Eyes http://www.mobygames.com/game/3x3-eyes-seima-densetsu
Music (音楽) Kaoru Wada (和田 薫), Yukifumi Makino (牧野幸文), Yoshiaki Kashima (香嶋良昭)
Milpo was also nice enough to include the CD soundtrack (KICA1123/1124) http://vgmdb.net/album/1558
The OST credits the three as follows on Booklet pg. 3:
作曲.編曲:和田 薫,みるぼ,MACKY [Compose & Arrange: Kaoru Wada, Mirubo, MACKY], which becomes
[Compose & Arrange: Kaoru Wada, Mirubo, Yukifumi Makino]
Therefore, Milpo/Mirubo = Yoshiaki Kashima