Like Kikaider, my reviews for this series will be split in half. On this side, the "blue", good side, I will focus on the positive. Negative aspects and spoilers will be shifted to the "red" side in the comments section.
6 months have passed since the previous volume. At an environmental conference, Gil delivers an ultimatum: the human race must give up technology or be destroyed. Gil then has one of his robots attack the ship the conference is being held on. Mitsuko orders a man named "Ichiro" to change, who then transforms to a human sized Kikaider 01 model. Another robot appears and kills Gil. This robot calls itself a Shadow Knight and that it works for an organiztion called Shadow. Gil appears again soon after.
Side story: Hinano has a teacher, Meiko. Dark is causing people to commit suicide via subliminal sound waves. Meiko is herself a robot (the cover girl) and apparently works for Shadow. (When she transforms, she looks like Bijinder from the Kikaider 01 anime, but she's never called this.)
Note: Amazon is confused. It won't let me post separate reviews for volumes 4, 5, and 6. This is the review for volume 5. I'll try to post my review for volumes 4 and 6 as a comment to my review for volume 7.