Abnormally Normal
The plan succeeds: all the witches are instantly transformed into mice, and then killed by the hotel staff and guests.
After returning home, the boy and the grandmother come up with a plan to use the potion to eradicate all of the witches in the world. The boy is still a mouse, and will only live another nine years; but he is not concerned by this, since he will live as long as his grandmother."
"Yikes! What kind of ending is that?" I asked frightened
"It's not so bad"
"Are you serious it's very much worse, how could you not have nightmares, he couldn't even let the boy turn back human, he had to remain a mouse-like anyone would be okay if they turned into a mouse"