Eru no Rakuen [Side: E] was the song of the Elysion Story Suite. The song was performed by Aramary who acts as El and Jimang who voiced as the masked man or Abyss. This works as the story's prologue and explanation to how the masked man starts getting sinful ladies whom she thought to be her daughter.
Aramary - El (aka "Elys")
Jimang - Abyss (The masked man and El's father)
El is a seven year old girl with a fatal disease. As soon as El's birthday is about to come, she asks her father a picture book as a gift for her. But El realizes all she want is to be with her father, so she often asks what would paradise look like. Then before her birthday, Abyss goes out to get the picture book El is asking for. He does a gruesome "job" of killing a man in a wedding, but the bride stabs him and he crawls, bloodied, towards home only to find El dead, and it is implied he died alongside her as well. In Abyss's case, where he is in the land of the dead, made it his duty to "find" his deceased daughter. Along the way he encounters five girls whom he thinks might be his daughter, often asking before song starts "Perhaps....she is my Elys".