Proofs of interlinking relations between Tasogare-iro, Fukanzen Ilis and Hyouketsu Kyoukai

I've seen comments doubting on the relationship between Fukanzen Ilis and Hyouketsu Kyoukai no Eden. Well, just to set things right, Fukanzen Ilis is a prequel to Hyouketsu Kyoukai no Eden, set in the same world a thousand years ago before Hyouketsu Kyoukai was casted.

I'll post some images and show some HEAVY SPOILERS using the images from some of the volumes. And I mean it. So for those people who does not want to be spoiled, turn away now.

Review: Tasogare-iro no Uta Tsukai (黄昏色の詠使い)

"Garden of Corrupted Song <Eden>; The Huge Tree that Bears Red Fruits <Nexus>; Capital where Stars are Dreamed <Reinenhabe> - any one of those names are right, and each has their very own meaning. However, should you want me to come up with a name for our current place right now, I'll call it 'Garden of Serra'. This is the blank area where all Recitations are created and return to." —— Xeo