Kazuki took in a puppy that was on the verge of freezing to death on a cold rainy day in the middle of winter. He also let in a stray black kitty that often came to play with him. He welcomed both of them into his room and gave them food and warmth. Before he knew it, he fell asleep to the faint sound of raindrops and the whir of the heater.
When he woke up the next morning, there were two naked girls by his side. It appeared that the animals had turned into humans and wanted to repay him for his kindness.