Remembering (Book 4 of The Starlight Chronicles

After starting 11th grade, teenage sort-of superhero Hamilton Dinger has not made peace with Starry Knight's seeming betrayal. But as the remaining Sinisters work to finish their mission, he is unable to avoid her. Working alongside Elysian, his changeling dragon, and Aleia, the Star of Memory, Hamilton has to find a way to overcome his hurt in order to save the day.