Mazinkaiser vs the Great general of darkness is a retelling of 1974's Mazinger Z vs. The Great General of Darkness. The new Mazinger Team is overwhelmed by the surprise assault of the subterranean Mykene empire resulting in many casualties, but Mazinkaiser ultimately defeats the forces of evil, ending with a bitter duel against the leader of Mykene, the Great General of Darkness.

In the last chapter of the Refrain Blue series, the bond between Yoshihiro Matsunaga and Nao Morisawa grows stronger, while Yoshihiro finally finds out the identify of the mysterious girl from the first chapter.

The first chapter of the Refrain Blue series, tells about the recollection of Yoshihiro's past about various events of summer school, of the fate where encounter and separation are interwoven with each other, as Yoshiro and Matsunaga will pass the Toyo Gakuen and will arrive at summer school at seashore. A mysterious girl smiles as she watches Yoshiro who stands still at the seashore dusk.

The second chapter in the Refrain Blue series focuses on Nao Morisawa and the events that happened at the summer camp last year, with her and Yoshihiro Matsunaga both unable to let go of feelings of the past.