These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Complete Monster: Cain. He's raped and murdered hundreds of innocent people, watched as a newly transformed Shido slaughtered his hometown in a feeding frenzy and then erased Shido's memories to the point that he couldn't remember his own name, tortured a reluctant Nightbreed who was in severe denial and only wanted to see her lover back from war, fatally slashed Riho after he believed her to be a rival for Shido's affections and trapped Shido in an illusion where his worst nightmares of pain and loss came true.
Die for Our Ship: There are those who don't exactly care for the Shido-Riho pairing.
Evil Is Sexy: In episode 12, after Riho leaves Shido, she starts dressing in a slinky black mini-dress.