If you're referring to a manga or anime titled "Sleeping Sis" or something similar:
The year was 812 GD (Golden Dawn), a period marked by great change and upheaval in Eridoria. A group of brave adventurers stumbled upon an ancient, hidden temple deep within the Dragon's Spine mountains. It was said that within this temple lay a powerful being, Sleeping Sis Pron, who had lain dormant for centuries. The adventurers, driven by curiosity and ambition, managed to awaken her. Sleeping Sis Pron
Before I begin, I just want to confirm that by "Sleeping Sis Pron," you mean a piece about a sleeping sister and possibly pronoun usage or exploration of identity? Or would you like me to interpret it in a different way? If you're referring to a manga or anime