Yesterday I got the tankobon volume of the two spin off manga (Guren Gakuen-hen and Spiral Boy).While I still can't read them properly, I gave them a first look and noticed the omake pages added for the volume release. I thought someone could find them interesting and scanned them ph33r my skillz. The Guren Gakuen-hen omake pages are two illustration eye-catch style and a handwritten afterword with a cute picture of Nia and Yoko, while the Spiral Boy ones are a rough sketck, a sort of Imageboard (with a couple of fanservicey Nia shots, be warned) and the afterword by the author. To see the pictures in full click on them.