- Arc Fatigue: The massive flashback arc surrounding Shicmuon's parents. After awhile, many readers became impatient wanting it to end just so that it could finally return the focus to the present cast.
- Base-Breaking Character: Shicmuon. For many, he's a good-looking Ax-Crazy badass that provides the series a plethora of Ho Yay moments with the main character. For others, he's a boring Flat Character that has no depth whatsoever outside of his insane obsession for said main character.
- Ho Yay:
- Shic is obsessed with Blow. Ob. Sessed.
- Rood and Lidusis have their moments, too, what with the former's job being to protect and befriend the latter. Of note is the instance in which Rood suddenly tears open Lidusis's shirt while the latter is sleeping. (He was looking for a magical mark on his body, but still.) Things continue on a little awkwardly between the two of them for a few days until Rood has to explain that he didn't mean it that way.
- Dio and Rood have had their dorky bromance moments from the start, but ever since Rood was revealed to be the King, Dio, a devoted follower from his past, has threatened anyone away from touching his beloved master and is dead-set against "repeating the stupid mistake of losing him again".
- Launcher of a Thousand Ships: Many fans seem convinced that Rood and/or Blow is going to end up with a harem due to his general badassery, and it's not at all out of place to see him shipped with the likes of Lidusis, Dio, Shic, Lin, Iel, Tessi, and even Master, to name a few.
- The main character being named Blow can be hard to take seriously for one very obvious reason.
- A large amount of reader's find Lispen's three demon wings hard to take seriously since the "third" one just awkwardly sticks out the center of the back. A lot question how said third wing is supposed to help with flight given its placement.
- Viewer Gender Confusion: To the point that even the wiki site didn't know if Professor Kan is male or female. It's eventually revealed he's male.
- The Woobie:
- Lidusis is a bit of a Stoic Woobie in that he rarely expresses how he's feeling outwardly, but it's very clear he's suffering on the inside.
- Chevel goes from simply Jerkass to Jerkass Woobie when it's revealed that the reason he bullies Lidusis is because he blames him for his younger sister's sudden and brutal death. It doesn't justify his treatment of Lidusis by any means, but it certainly does put his cruelty into perspective more. (Furthermore, after Lidusis saves him from Professor Heil, he acknowledges he was wrong in how he treated him, lays off the bullying, and genuinely seems to be on the road to becoming a much nicer and more laid back person.)
- The Helios Academy students overall could be seen as such given the amount of times they've been put into danger. They've fallen into Professor Heil's trap during the Ishuella incident, they then get attacked by Demons at Helios Academy, and then they get sent off to the Magician's Tower where they get attacked again. It gets to a point where you feel like these students are going to be traumatized for life once things are back to normal.
- And then we have an Iron Woobie in Kielnode Chrishi, who was horrifically abused as a child but who went on to be a devoted and loving father figure for his younger brother Rood, despite all the undue suffering he's endured.
YMMV / Black Haze