Hybrid Heaven, Konami's 1999 N64 adventure / RPG / fighter hybrid is, in parts, one of the most interesting games of its generation.
'Basically, I thought of creating an RPG battle system, but since the game is 3D, I needed 3D fighting action elements. And in real fighting, it's not just a case of punching and kicking, it's also a case of thinking and action at the same time. So I wanted to describe that in the fighting system. So, for the action, it's the moving parts, where you face your enemy and so on, and for the thinking part, you have to think of the command to come up with your moves. So yes, I think we've created an intelligent new-style RPG battle system.'1)
- Yasuo Daikai, Hybrid Heaven director.
The main designer shaven't worked on two much else in a design capacity(according to MobyGames), but two of them (Yasuo Daikai and Tetsuya Matsui)did work on Coded Arms for the PSP.
The first footage of Hybrid Heaven was quite different to the released game. Most noticeably the player's character has a different design, and there are some handsome flat-shaded polygons—much like Konami's first Castlevania 64 footage. Most probably the footage comes from target renders on Silicon Graphics hardware and is not actually running on an N64.
For more details see this page on Unseen64: