A Sepia-colored Promise with a Sleeping Girl: A Trick?

Keitaro discovers a doll that can move on its own. Everyone is amazed by it but Keitaro seems to be able to hear it talk also. He finds out from the doll that his great grandfather promised to fix its legs but never did and being the good guy he is, Keitaro decides to fulfill his ancestor's promise.. With the help of the girls, of course!