A Book by a Pony

Looking for a Novel!!! I Stumbled Across It and Really Want to Read It! Please Help Me Find It

The general plot is that in their previous life, the gong imprisoned the shou and treated him very well. But the gong died for some reason (the recommendation video didn't say why), and the shou was free. Later, though, he remembered how good the gong had been to him, then was reborn and found himself back at the time when he was imprisoned. Something like that.