High school student Nanase has a dream that he keeps seeing. That dream contained memories of his past life and there, Nanase was a knight who faithfully served his precious master. Nanase doubts whether those memories are real, but one day, Leo—his master—transfers into his class as Reo. Reo also has memories of his past life and is simply happy to reunite with Nanase. However, he forgot the most important thing. To Nanase, he is the last person he wants to see—