Using the same method as for Yoshitaka Suzuki (info from here +
http://5pb.jp/records/release/detail...code=VGCD-0136 ), I found how his name is written in japanese, and it's イズタニタカヒロ
Seems to be the way it's written everywhere, like here :
http://www.gem-impact.com/profile_izutani.html
And there's also a picture there.
So I think this wraps up the search for the MGS4 OST's composers' japanese name. (by the way, some still haven't been added, I don't know if this was because they were wrong or just because no one has gotten around to do it)