Ryotaro thought about it while watching the Imagin float about.

"The Imagin... are kind of... powered by memories..." He said, carefully trying to word out his explanation. "Without a connection to a human with strong memories, they can't keep existing. Their appearance is tied to their host's imagination, and they can only take physical form in the present if they are granting a wish for a human. They try to grant wishes for people in exchange for using that person's strongest memory as a link that lets them fly to the past." He paused for a moment, sorting it out in his head.

"Not all of them are like that, though. My friends never made a real contract with me, they just connected to me and helped me. And another friend of ours, Sieg, made a contract with a mother to protect her baby, and didn't care about going to or harming the past."