A theme that I've noticed is mystery. Lyon might have a mysterious past or a secret power, and the reader is drawn into that mystery. As they try to figure it out together, their bond deepens. It adds an element of intrigue to the fanfiction and keeps the readers hooked.
One common theme is adventure. Often, the reader and Lyon are on some sort of journey together, facing challenges and growing closer as they overcome them. Another theme is self - discovery. Through their relationship with Lyon, the reader might learn more about themselves. For example, in some stories, the reader discovers a hidden strength or a new passion.
Love and friendship are also big themes. The relationship between Lyon and the reader can start as a friendship and gradually turn into something more romantic. There's often a lot of fluff and sweet moments in these stories. Sometimes, there are also themes of sacrifice, where either Lyon or the reader is willing to sacrifice something for the other's well - being.