Chaosic Rune

The story begins with the protagonist angsting over the death of his parents in a plane crash. The primary cause of said angst is that he was the only survivor of that crash, and the remains of everyone else had been eaten. A mysterious man invites the hero to come with him, claiming to have the answers to the questions the young man has. The young man is taken to a facility up in the mountains, and is placed in a room with several other young men. A set of cards is dropped into the room, and the first person that picks up a card suddenly has a monster emerge from his guts. This person has the monster go on a killing spree, and soon a battle royale begins. What is going on with all these strange cards? Where are these monsters coming from? And why does this seem eerily similar to a children's card game?

There is a sequel, and it is even more bloody.

This series provides examples of:

 * Black and Gray Morality: Well, the hero and (most of) his posse are decent folks... but they're pretty much the only characters who aren't Jerkasses at best.
 * Cannibalism Superpower: Death Rex. Look down at Mega Manning for the first half of his powers. The second half is that by eating people or monsters, Death Rex heals his controller.
 * Deader Than Dead: Anything and anyone eaten by Death Rex is explicitly gone, utterly and completely annihilated, body, mind and soul. And Death Rex wants nothing so much as to devour everyone and everything.
 * Deconstruction: This is the "Children's Card Game" anime series' deconstruction in full force.
 * Eldritch Abomination: Death Rex, whether whole or its individual pieces. Other powerful "Dragon" type monster can qualify as well.
 * Extreme Omnivore: Death Rex. He can eat everything, and if he eats something, it disappears completely from the world. This means that if he eats an opponent's monster, that monster's controller disappears as well.
 * Grimdark: The protagonist believes he ate his parents. The Token Mini Moe of the team starts off wanting to murder the hero, believing he's the one who killed her brother. After the first arc, mass murders tend to occur every time a new villain appears. It's like if someone took the Grimdark out of Warhammer 40k and put it in a playing card game series.
 * Sequel's worse for the record.
 * Humanoid Abomination: "Magic" type monsters.
 * Infinity Minus One Sword: Death Rex, the protagonist's strongest creature, is normally an Infinity Plus One Sword, but was divided into pieces, each one incredibly powerful, and each piece wanting to be the dominant part when they come back together (several of the pieces blame the head and mouth, the piece that the hero has, for their being divided in the first place).
 * Kid With the Leash: The only reason Death Rex isn't eating infinity right now is because the kid has control. When the kid tries to gain more control over him, he has to fight Death Rex with his other monsters. It doesn't go well.
 * Gorn
 * Mecha Mooks: The Machine Society's card monsters fall under this category.
 * Mega Manning: Death Rex, once he defeats a former part of himself, allows the hero to summon that part of Death Rex. And if Death Rex devours a monster, the hero gets a card allowing him to grant Death Rex with that creature's power for a short time.
 * Mind Rape / More Than Mind Control / Brainwashed and Crazy: When the main character fights against Death Rex in order to establish dominance, Death Rex doesn't even need to attack: he violates the hero's mind until the kid goes temporarily insane, decides to end it all, and just has Death Rex go on a rampage (which is what Death Rex wants to do anyways).
 * Names to Run Away From Really Fast: DEATH REX. Doesn't get any more obvious than this, folks.
 * Our Dragons Are Different: "Dragon"-type monsters, which tend to not look at all like something you'd consider a dragon, bur more like Starfish Alien bioengineered living weapons; the strongest one, Death Rex, as well as its separate parts, is a full-fledged Eldritch Abomination.
 * Rated M for Manly: Excessive gory deaths, big muscular men, well endowed women, cards that summon weapons such as swords, pistols, and shotguns. They may as well call this series "Testosterone: The Card Game".
 * Sorting Algorithm of Evil: First there's the villainous prospective Dragon Card users in the pseudo-tournament, then there's the Machine Society, then the Magic Clan... and to top it off, even though the situation with the Magic Clan still isn't resolved, . The first series ends on this little cliffhanger.
 * Verbal Tic: A running gag (possibly from the translators) in this series, several villains tend to have a sort of mad libs catchphrase. Examples include "Have you ever seen the movie X? I haven't, but it's kind of like that."