[Shikamaru blinks at that, taking it seriously for a moment. Then he wonders if that was a joke or him still being bitter.

He shakes his head and adjusts his knees on the log.]

Besides that, one of the reasons we're starting with this jutsu because it's the most similar to what you already know. Via summoning and storing items in scrolls, you've already worked with displacement.

Substitution is trading places with an object. In a sense, you'll be displacing yourself.