[That's because he stole it figured it out. And improved it. (or so he feels.)]

"Maybe I'm just not concerned about a you from 'another world' talking about it. You obviously already know- and you're not lying..." [Who would dare?] "So there's nothing for me to worry about."

[Pause.] "...I'm still not a 'creature'. Or a 'supernatural entity'..." [...Actually wait maybe he is.

But Kaito is NOT, and THEREFORE...]