Very similar plots : In distant future, an Outlaw / Rebel gets chased down by the authorities and bounty hunters for being the most wanted head in history.
The main characters also look physically very similar : spiky hair, red coat, mechanical hand, black hands and shoes
Both of the anime have one guy whom unrivaled groups had been hunting for some reason. One knows why he was being captured (Blazblue) while the other does not (K). Both shows are 'epic-ly' drawn and animated. Both stories are interesting and are shounen and supernatural. Both anime has a very nice soundtrack and a choice of voice actors. And both of them can be enjoyed very well.
Both have Yandere characters. Blazblue has Nu-13 and Mirai Nikki has Yuno. Both are battle oriented and have a bit of a romance going. Both are about capturing and defeating opponents in either a survival game(Mirai Nikki) or a bounty(BlazBlue) Both have good detail in terms of animation and are epic, even though BlazBlue is more of a supernatural anime and Mirai Nikki falls more in the line of a psychological thriller.