Both anime have a similar feeling, both are psychological with philosophical content and discussions. Both anime have a main character that has more personalities than 1, both are called Shiki and both are very mysterious and hard to figure out.
Both anime have a mysteries to solve.
Main difference; Kara no Kyoukai deals with magic, Subete ga F deals with online/high tech things
Artwork in both anime have great resemblances, due to the fact that both stories are written by Type-Moon. These anime feature a world where magic exists, and can be used be a given few people. Furthermore, the female protagonists are sword/knife-wielding bad-ass without descending into the usual dere stereotypes.
Both have protagonists who undergo events(many of those events are unclear at first), which coerces them to change themselves radically to, both survive, and achieve their goal(s).
Both stories are quite mysterious in the beginning, but become clearer through clever, and acceptable explanations. The twists all come fruition during the climax.
Both have great art(more so leaning towards Kara), and relatively captivating soundtracks.
KnK 4's central mystery directly relates to it's prequels and doesn't answer anything other than that... KnK 4 shows how the lead gets to where she is, throughout the majority of the overall plot, but doesn't describe much else.
Eureka Seven's development of character is a primary, but not the only focal point. Also the events revolving around the plot, are explained wholesomely, but still haphazardly. read more
The main leads are unexpectedly thrusted into a predicament that radically alters their being and sense of self throughout the story.
In both cases, the lead had a COMPLETELY different lifestyle that, while not perfect, was something they were, near-constantly, desiring during the story.
However... the lead(s) go through a self-journey to realize the changes and to make peace with them. Resulting in remarkable and inspiring developments.
Both are also bloody, gory, violent, and look and sound PHENOMENAL.
KnK 4 is part of a chain of movies that, while entertaining by itself, should be watched in order to get maximum comprehension. The aspects and plotline however, greatly correspond to Blue Gender's main character's journey.
Blue Gender, in addition to many more themes, deals with the hero's struggles to adapt, and comprehend with whats going on. His disposition virtually changes, but, like KnK 4, his primary existence remains... read more