So maki is basically confirmed with lieutenant...
Shinra could possibly end up with Tamaki or Iris, although I think Iris has more significance in the plot so if the author doesn't end up killing her for plot purposes she might be end girl. Unless the story has a low romance and ends up with Shinra leaving solo to deal with the Nether or something.
Captain Obi and Captain Hibana probably won't have an ending, neither will Arthur