 If you liked
Zetsuen no Tempest
|
 ...then you might like
Guilty Crown
|
Both have a virus that kills people by transforming them in crystal/metal. Both have a main guy with a deceased sister. Both have two male best friend protagonists: a blonde guy which is a badass and a brown haired guy that does not wishes to fight. Both have an extremely powerful girl with magical power as heroine, and in both the theme is "save the world".