Chrome was a magician in the heros party.
He fought the Demon Lords army alongside people like Irina, the lover who vowed to marry him in the future, and the hero, Yuno, who was his close friend.
They were all close companions. However, that was only in Chromes mind.
His lover, Irina, became intimate with the hero, Yuno, and Chrome was sacrificed to make the hero stronger. Chromes magic powers were snatched away and he was kicked out of the party. Demons surrounded him as he was on the verge of death and he was driven to a corner.
At that moment, Chrome awakened to a darkness within himself.
Amidst his despair, he acquired an unrivaled skill.
Now with this skill, he could exact revenge.
- Asshole Victim: The rest of Chrome's party. One might think that the betrayal Chrome experienced in chapter 1 was Necessarily Evil and the rest of the "heroes," at least some of them, would otherwise lead heroic lives since they used the power they stole to defeat the Demon King and save the world. Nope. Once they got the glory and fame of the accomplishment of being the first of seven parties of "heroes" to pull it off, they spent the next two years engaged in all sorts of atrocities, especially the warrior, Riot, who is granted a Duke title and goes The Caligula, running his fief with a Reign of Terror, beheading any and all male servants for the slightest inconveninence, real, imagined, or invoked, and raping any and all women he gets his hands on, to death. Irina, Chrome's fiance, who lured him into the trap in chapter 1, continued being The Vamp, using her sex appeal to gain power and prestige, and then once she's accomplished her objective, discarding the men she used, as trash, and should they object, uses brainwashing magic for a bit of Psychic-Assisted Suicide so she can remain a Villain with Good Publicity.
- Crippling Overspecialization: Literally. The curse Chrome's party casts on him in chapter 1 leaves him so crippled, his bones are as fragile as glass, and he can only limp along at such a pace, an old man in a wheelchair can outrun him. On the other hand, he's got an aura that does fixed damage once every three seconds. After a two-year Time Skip, this damage has reached 9999, and can affect anything Chrome sees as an enemy, or which sees Chrome as an enemy, including magic, making him an all but unstoppable Advancing Boss of Doom with an "Instant Death" Radius.
- Driven to Villainy: Prior to his betrayal, Chrome was a decent and upright man, who would have sacrificed himself to keep his friends and loved ones safe. After, he's a withered, broken, old man who is forced by the curse cast upon him to go after his former companions for revenge, just so he can survive.
- Evil vs. Evil: The seven parties of chosen "heroes" versus the Demon King and his flunkies. The Demon King's armies are omnicidal and practice Rape, Pillage, and Burn while the so-called "heroes" are merely glory-seeking thugs vying for supremacy over each other and won't hesitate to engage in any villainy they think will give them an edge. Chrome learns this last part a bit too late when his own magic mentor curses him with "The Chains of Despair" to not only steal Chrome's power away and hand it off to "The Hero" Yuno, but afflict Chrome with "Darkness" to empower Yuno with "Light" that the Demon king and his ilk are weak against.
- Revenge: The primary motivation of the plot. Chrome is not alone. Riot and Irina are on-screen abusing the commoners and their subordinates to the point that they, rightly, want homicidal revenge, both because the treatment is that bad, and because their lives depend on it.
- Villains Want Mercy: Without fail, whenever Chrome catches up to the so-called heroes who betrayed him, cursed him, and abandoned him to be Left for Dead, rather than flee for their lives, they beg, plead, and grovel for mercy. Unfortunately for them, Chrome has none to give at that point, and they've burned through whatever sympathy they may have had from everyone else, on both sides of the fourth wall.
- Yin-Yang Bomb: While most people think [Light] and [Darkness] attributes are antithetical to each other and will mutually annihilate, that's wrong. They may be mutually antithetical, but they feed off of and strengthen each other when they clash, and they have a tendency to fuse into [Chaos] which precious little can stand against. Chrome and Yuno learn this by accident when they clash both with each other and with other wielders of their respective opposite element.