Both have the theme of some sort of 'Serial Killer Gene' (that in some cases is a 'Genius Gene'), and somewhat explore the ethics using that knowledge

Both are about solving crimes, though Mouse is more about a big overarching case, while Justice in the Dark seems to be broken up into smaller cases that are connected (once it's fully released, this might be different)

Mouse does not have any BL themes, and seems to be more graphic when showing crime scenes