Saint Maiden's Day on Aprica Nova

The venatores gemini are a unique class of legionnaire. Linked from birth with a spiritual twin, these warriors are the Imperia's best weapon against the deadly sirens.
  Gemini pair Titus and Gnaeus are exceptional venatores. Even so, every hunt is life-threatening. And when they find themselves separated on the barren planet Aprica Nova in pursuit of a fleeing siren, Gnaeus realizes this hunt might be their last.