What Only the Stone Slab Knows [Crossover]

During the summer vacation of 2014, when I was seventeen, I found an ordinary-looking white stone on the coast of Kanagawa. Later, I learned that the stone had once belonged to a massive stone tablet called the Dresden Slate. They say it was once a very magical sacred relic. And so, an ordinary person like me spent this summer dreaming a very long dream, a dream only the Slate knew. Reading notes: 1. I haven't written fanfiction in ages, but suddenly really wanted to tell this story. It was a spur-of-the-moment idea, and I'll write whatever comes to mind, with no outline and no constraints. 2. The story is low-key and mild. 3. There's very little information available about some of the characters and plot points, or I couldn't find any. Please forgive any out-of-character moments or mistakes, and feel free to point them out. 4. Fandoms involved: K, The Prince of Tennis, and others to be decided. Theme: Love can give people the strength to keep moving forward.