This card sucks! I didn't realize you had to have the actual monsters on the field to use this card. I wasted keys for paradox trying to use this on lvl 30.
What's printed on the card: "Using monsters you control as fusion materials"
What it SHOULD say: "Using the required fusion materials"
with a name like "fusion substitute" it's easy to misinterpret the meaning. I thought the same as Trunks at first, and wondered if that's really what the effect was, which led me to look up the official rulings.
Trunks
Not KoG