What is a short summary of the story, Super-Frog Saves Tokyo, from the collection, After the Quake?

Super-Frog Saves Tokyo is about a man named Katagiri who works as a collections agent for a bank and is primarily tasked with upholding the debts of the criminal underworld. One day, he comes home to find a giant anthropomorphic frog in his kitchen, who goes only by Frog. Frog insists that Katagiri needs to help him save Tokyo from an earthquake of its own that will be caused by an entity called Worm. To show he is serious, Frog assists Katagiri in his work. Katagiri agrees to help Frog, but on the evening before the battle, he is shot while making his collections. Katagiri wakes up in the hospital, where he is told that he was not shot at all, but suddenly entered a coma for reasons the doctors cannot explain. Frog appears to him that evening and tells Katagiri that he was in a coma because he was assisting Frog with fighting Worm. Frog is severely wounded and dies a gruesome death before Katagiri suddenly jerks awake. He tells the nurse about Frog and mournfully says that he has gone back to the mud.