No. The official Totoro franchise is known for its positive and heartwarming stories. The 'Totoro Dark Story' is likely just a fan - created or alternative interpretation that has no official standing within the franchise.
One of the novels that matched the description was " Fairy Dragon Girl." The female lead of the novel was named Chu Yue, and she had a pet that looked like a Totoro. Chu Yue was a dragon trainer. She trained all kinds of dragon girls, including the big demon dragon. In this novel, the female protagonist's pet dragon had intended to eat her Totoro.
I recommend the book "Possibly a Fake Silver Soul". It tells the story of Jiang Cheng, a transmigrator, who met the owner of Xinghai District and his girlfriend, Jiang Hua, who were traveling in the universe in the dragon vein of a certain planet. Later, he came to Earth and met his teacher, Yoshida Shoyo, who had influenced his life. He also met a group of friends. This included the transmigrator Okita Soki. This is a Silver Soul Doujinshi novel, don't miss it. I hope you like this fairy's recommendation. Muah ~๐
A normal Totoro story focuses on the magic and wonder that Totoro brings to the children's lives. However, a scary Totoro story often plays on our fears of the unknown. Totoro in a scary story could have hidden motives or be a symbol of something more sinister. The mood is completely different. In a normal story, it's warm and fuzzy, while in a scary story, it's tense and full of dread. There could be elements of the supernatural that are not so positive, like Totoro being a spirit that is angry or vengeful.
Gintama is purely fictional. It's filled with imaginative characters and scenarios that are not rooted in real-life events. The creators crafted a unique and entertaining fictional world for the audience.