The songs "Saika", "Sacred", "Sanctity", "Holy Knight", "Colorful Skies", and "Bloody Purity" all appeared in the arcade game Mozarc: Fall in Melody.
"Hot Air Balloon" is the main theme to another Rayark game, Mandora.
Young versions of Iris and Rosabel from the "Holy Knight" cover can be seen in the crowd of the cover art for "Sweetness Overload!!!", as well as Deemo, Alice, and Celia from Deemo and Queendora and some Mandora from Mandora.
The red and blue haired women from the cover of "Holy Knights" are named Rosabel and Iris respectively. Chapter K is dedicated to telling the story of these two princesses, with all songs being variations of "Holy Knight."