Question about song performer (from Might Gaine)

I’m sure there are people here who know the mecha anime Brave Express Might Gaine. …I’ve been a bit stumped recently on the performer of "BLACK DIAMOND", the ending theme to the show – even Japanese Wikipedia claims that the performer of said song, Purple, is actually voice actor Katsumi Suzuki.

However, I’m not entirely sure if that’s true. Suzuki has no other songs under his name which makes me question if he even CAN sing, which would make Purple’s singing voice someone else. Would anyone happen to know who actually, REALLY, sung BLACK DIAMOND? It’s been bothering me for the last few hours and Google doesn’t help, even in Japanese.

EDIT: This is the song in question. It really sounds more pro band level than voice actor level. https://www.youtube.com/watch?v=YNFyhiEesuA