Three years ago, mysterious giant demons called Kijuu have started to rampage throughout Japan. The only one who can fight them is a comically strong and hard-boiled rooster named Keiji who seeks revenge on them. Along the way, he meets other animals who are just as brutal and intelligent.
Rooster Fighter features examples of:
- '90s Anti-Hero: Keiji is a superpowered rooster who brutally murders demons, tries to mate with every chicken he meets, and acts as a Jerkass to everyone unless they impress him.
- Absence Makes the Heart Go Yonder: Before leaving town, Keiji recalls that he left a chicken crying and goes to see her. She's already mating with someone else despite it only being a day, so he leaves quietly.
- Affectionate Parody: The manga takes the classic superhero format, but the hero is a supernaturally strong and perpetually angry small animal.
- Artistic License – Biology: While chicken do have fingernails, Keiji's and Elizabeth's legs looks pretty much like four-fingered human hands.
- Bait-and-Switch: Several times in a row, it looks like Morio is holding the dam, but it collapses anyway, and it takes several attempts for Keiji to block the river with a boulder. Turns out Morio survived, only to immediately get brainwashed by a devil.
- Big Damn Heroes: After a temporary Breaking the Fellowship, Keiji returns to save Ibokura from falling off the dam.
- But for Me, It Was Tuesday: Elizabeth is another chicken Keiji left after sleeping with, and he doesn't recall meeting her before at all.
- Carnivore Confusion: Keiji is really offended by being offered a KFC stick from a little girl.
- The Casanova: Keiju's habit of getting intimate with chickens not only got him a few enemies, he's not even above dating pigeons if they ask for it.
- Child Hater: Keiji dislikes children, human or bird, for typically being abusive idiots, but he's not above defending them.
- Clingy Jealous Girl: Piyoko is a baby chick who worships Keiji and wants to marry him, and doesn't enjoy the company of Elizabeth.
- Cocky Rooster: Keiji the rooster can be extremely prideful, and him holding grudges often gets in the way.
- The Comically Serious: By just being a rooster, Keiji turns every scene he appears in into a comedy by treating every situation with intensity, sometimes even bewildering his companions.
- Compelling Voice: A demon emerging from Sei's father hypnotizes villagers to dig up treasure for him.
- Cool Old Guy:
- An old man shelters Keiju from violent kids and feeds him, and even tries to shield the same kids from a demon.
- An old toucan lets Keiju sleep at the zoo, despite not being a zoo animal. He tries to fight a demon for disturbing his Family of Choice and dies while being honored by them.
- Dirty Coward: Usyo's Yakuza partner says he's decided to start a legal company and asks him to sign a paper for it. Turns out the paper is actually labeling the receiver of an old loan, and soon Loan Sharks arrive and say they don't know anything about the other guy.
- Disowned Parent: Keiji refuses to help his half-brother Keisuke to rescue their father because he has abandoned his mother dying and is implied to have left for demon-hunting.
- Establishing Character Moment: The series starts with Keiji saving a child from a demon like he's a Superman, then flashbacking to him mating with a chicken he melodramatically leaves behind.
- Extreme Libido: Keiji has a supposed special condition called Lord of the Rut that requires him to mate with someone twice a year or he'll get violent. His father was no better.
- Face of a Thug: A former Yakuza scares schoolgirls away by trying to sell them baby chicks he's been taking care of.
- Famed In-Story: Due to Ibokura's livestreams, Keiji actually gets known as a hero.
- Fantastic Racism: The turtle hates all birds because seagulls ate his baby brothers.
- "Fantastic Voyage" Plot: Piyoko volunteers to get inside Morio to remove a parasite from his brain.
- The Gambling Addict: Sei's father has lost everything to horse races and believed that he'll make everything back by searching for buried treasure for a year. He didn't succeed.
- Go for the Eye: A good way to stun a giant demon is to poke it in the eye.
- Going for the Big Scoop: Ibokura is a ViewTuber who found a superpowerful rooster to be his goldmine to boost his channel and chases after him despite the danger of demons, because he can't stand his coworkers criticizing him for not doing his job. After being impressed by Morio and Keiju, he starts changing for the better.
- Groin Attack: Elizabeth temporarily fixes Keiji's Extreme Libido by kicking him where it hurts.
- Healing Factor: The Nume demon quickly regenerates from Keiji's attacks by hiding its organs in its tail. He just increases his range until there's nowhere to hide.
- Hot Springs Episode: Chapter 8 features the team going to hot springs to heal wounds and doesn't have any fighting.
- Idiosyncratic Episode Naming: Chapter titles are derived from bird-themed proverbs.
- I'm a Humanitarian: Demons are generally unintelligent giants who aim to eat humans, unless they are overwhelmed by some stronger desire.
- Improbable Aiming Skills: Keiju catches a flying bug by spitting a pebble at it.
- It's Not You, It's Me: Keiji leaves a chicken he just slept with, not because he thinks of her as a toy, but because he's a "wanderer" and it's mating season. She's left heartbroken anyway.
- Kid Sidekick: Impressed by Keiji's justice, a little chick decides to follow him, who is initially not happy for dragging a kid along, but changes his mind and gives her a name Piyoko without thinking (meaning Chick).
- Nearly Normal Animal: All animals in the manga have human-like intelligence, but can only talk directly between each other. Elizabeth, a chicken, is even skilled at using the smartphone and at cooking.
- Not So Above It All: When toucan Zena offers Keiji food, he states that he doesn't deserve such kindness. Then asks for it when Zena tries to take the food back.
- Our Demons Are Different: Demons are eldritch Kaiju appearing from humans and even animals with The Power of Hate. An indicator if a human is become one is a bud on their neck, that bursts if they get angry. The monsterization can be undone in some cases. Then there are devils, shapeshifting humans who can control other demons.
- Playing with Fire: Sarah appears to be able to manipulate flames.
- Roundhouse Kick: Keiji knocks Tatsuo out with a 360 in the head.
- Rugged Scar: A bitter turtle has a scar over his right eye and is just as strong as Keiji, though he's weaker outside of water.
- Science Hero: As Elizabeth isn't as good in martial arts as Keiji, it turns out her weapons are developed by Yonesaka Group specifically for demon suppression.
- Secret Legacy: Keiji and Keisuke turns out to be descendants of the Goshikidori family, chickens specifically trained in Supernatural Martial Arts.
- Shock Stick: Elizabeth fights using a 10000V electric baton, and is pretty good at it despite having only one leg to stand on.
- "Shut Up" Kiss: Elizabeth swore revenge on Keiji for leaving her heartbroken, and attacks him disregarding the surroundings. He kisses her and she quickly joins his party.
- Sore Loser: In the past, Tatsuo has lost a fight with Keiji several times, then takes his sister Sarah hostage to ensure he'd win, which he still doesn't. Even a year later, he's still seeking "revenge" against him.
- Super Drowning Skills: Keiji can't swim and nearly dies when baby birds push him into a pond. He tries to excuse himself that he was practicing a new fighting style while screaming for help. He also tries to avoid a hot spring, despite it being pretty shallow.
- Super-Scream: Keiju's finishing move is inhaling air many times his size, and crowing so hard, glass and demons in front of him explode.
- Super-Speed: Keiju can move at supersonic speeds.
- Synthetic Voice Actor: Elizabeth can use a synthesizer app on her smartphone to talk to humans.
- Tattoo as Character Type: Impressed by a Yakuza tattoo, Piyoko asks her owner to give her one, and he writes "Justice" on her, which she's proud of.
- Tempting Fate:
- A nearby school holds an assembly to express gratitude to their pet chickens, only for rooster Tatsuo to monsterize right above them.
- Misuzu's grandpa says there were no floods in the village for 85 years. Cue the evacuation orders in a few hours due to the dam breaking.
- Think Nothing of It: Keiji tries to avoid mentioning that he heard the dam is about to collapse and was worried about companions he left behind, by saying he just happened to be there.
- Token Heroic Orc: While there are demons that instinctively help their community instead of attacking everyone, Morio stands out by being completely sentient, and turned out this way because his host got a call that his cancer diagnosis was mistaken right after giving to despair.
- Tsundere: Elizabeth hates Keiji's guts and can't admit that's what she likes about him.
- Wake-Up Call Boss: The two introduced devils turn out to be a lot stronger than the previous demon opponents, and their army of Brainwashed and Crazy demons means the heroes can't use their strongest attacks against them.
- Wham Shot: In Chapter 24 Piyoko gets Impaled with Extreme Prejudice, then manifests the same emblem as the white demon.
- You Killed My Father: Keiji's sister Sarah was eaten by an enigmatic white demon with a neck tattoo, which is why he hunts all of them down.
