"When my sister's like this, she's no joke."
"That's right. I'm not OP in this one. This is a story about my sister being OP."
— Asahi Ikusaba, laying out the plot for the viewer
One day, young otaku Asahi Ikusaba instinctively pushes a child out of the way of a speeding car and ends up getting hit himself. As his body goes into a coma, Asahi's mind is pulled in by a strange light. When he awakens, he finds himself in a world much like the High Fantasy RPGs he loves so much, with monsters, adventurers and guilds.
Overjoyed that he seemingly gets to live out his fantasy of being the overpowered hero in a classical Isekai setting, Asahi immediately joins the adventurers' guild of Epiphaneia and starts questing - only to realize that he's pathetically weak and way in over his head.
When a strong monster corners him, Asahi in desperation calls out for his older sister Maya. She appears - and proceeds to slay the monster with a single hit. Asahi realizes that it isn't him, but his sister who was reincarnated overpowered. And so the siblings team up to explore the fantasy world and find a way back home.
My One-Hit Kill Sister (異世界ワンターンキル姉さん〜姉同伴の異世界生活はじめました〜 Isekai Wan Tān Kiru Nee-san: Ane Dōhan no Isekai Seikatsu Hajimemashita) is a Japanese Web Serial Novel written by Konoe, which was released on Shousetsuka ni Narou from 2019 to 2023. Unlike many Japanese web novels, it has yet to be officially published in light novel format, but it has been adapted into other forms of media. It has an online manga with art by Kenji Taguchi, which was serialized in both Shogakukan's Sunday Webry website and the seinen manga magazine Monthly Sunday Gene-X from March 2020 to July 2023. A television anime adaptation by Gekkō premiered in April 2023.
Contains examples of the following tropes:
- The Ace: Maya's stats aren't only maxed out, they're so ridiculously over-leveled that they exceed her status window. And it shows. She effortlessly slays high-level monsters with a single attack without even breaking a sweat.
- Adventure Guild: Epiphaneia has one that Asahi immediately joins.
- Animation Bump: The anime adaptation's animation tends to become particularly fluid during fight scenes, especially in earlier episodes.
- Ascended Fanboy: Asahi's greatest dream was to go on an isekai adventure... only to find it is not as fun as he thought when his sister becomes the overpowered protagonist instead of him.
- Beware the Silly Ones: Maya's eccentrics and obsession with Asahi might make her come across as The Ditz more often than not. But try to hurt Asahi and she'll make you remember what this story's title is.
- Big Brother Attraction: Inverted with Maya, who's so obsessed with her younger brother Asahi that she willingly put herself into a coma so she could get Trapped in Another World along with him. She constantly hits on Asahi (much to his discomfort) and anyone who insults or endangers him will always be on the receiving end of her wrath.
- Big Sister Instinct:
- Maya becomes completely ruthless if Asahi's life is threatened, or even if he's insulted.
- Kilmaria develops this towards Asahi overtime as well as she nearly tries to intervene in a swordfight between Gloria and Asahi out of concern. She even incinerates a necromancer serving under another general of the maou when he insulted Asahi.
- Butt-Monkey: Asahi is laughably weak compared to his older sister and the rest of his eventual Battle Harem. Where they can slay high-level monsters in a blink, Asahi struggles against slimes and frequently has to either run for his life or beg one of the others for help. That's not to mention the constant unwanted advances Maya makes that Asahi futilely tries to fight off.
- Cassandra Truth: Gloria is correct to accuse Asahi of illegally going up in the ranks despite being weak physically and magically. However, no one believes her.
- Casting Gag: The King Great Shark in the Beach Episode is voiced by Nobuyuki Hiyama, who voiced a certain Shark Beastman. He also has a Transformation Sequence into a Humongous Mecha ala GaoGaiGar.
- Character Development: While still obviously weaker than his sister or any of the other girls he meets, Asahi ironically is getting stronger. During his fight with Gloria, while he doesn't lay a hit on her, his reflexes are faster and he is able to figure out a weak spot and uses the light spell he acquired to defeat her.
- Chekhov's Gun: While it appears lame that the light spell he receives amounts to being a mere flashlight, Asahi uses the same light spell to disorient Gloria during his fight.
- Curb-Stomp Battle: Every fight Maya enters has her steamroll her opponent in a single move. The only exception is Kilmaria, who is a high-level demon general.
- Death by Origin Story: Subverted. Asahi and Maya aren't dead, but their bodies in their homeworld are currently in a coma no one is sure they'll ever wake up from.
- Deconstructed Character Archetype: Asahi is a comical deconstruction of the Stock Light-Novel Hero, specifically the stereotypical isekai protagonist, as a nerd with low self-esteem and poor fitness. Realistically speaking, someone like him wouldn't be in the least bit qualified for a job that requires hunting strong monsters on the regular—and he isn't. His physical stats are about as laughable as you'd expect from an out-of-shape otaku, he's a poor swordsman due to never having actually held a weapon in his life and he tends to get himself into hot water because he keeps expecting the world around him to operate on video game mechanics when it only partially adheres to them. He also has no "cheat skill" to make him an Invincible Hero, with his older sister Maya becoming the freakishly powerful one instead.
- Didn't Think This Through:
- Asahi joined an adventurers' guild before assessing what sort of skills, if any, he possessed and whether they'd be useful for the kind of work an adventurer has to do. So he only realizes way too late that his stats are below average and that his only skill is throwing a stone a small distance away.
- Maya gave herself severe head trauma to follow Asahi to the other world but had no idea how to return after. This shocks Asahi, who assumed she'd come with a plan to get them both back.
- Dumb Muscle: Gloria is outrageously strong, but she tends to lack common sense.
- Fake Ultimate Hero: Asahi ends up becoming one unintentionally after Maya's defeat of the wyvern who attacked him and the Goblin Brothers are mistakenly attributed to him by the locals. This is a bit of a problem, as faking heroics to jump rank at the adventurers' guild is considered a felony punishable by death in Epiphaneia. Asahi has to ask Maya not to show her stats to anyone but him and keep making him look all-powerful if he doesn't want to get his head cut off.
- Hazy-Feel Turn: Kilmaria of Corruption, one of the Demon King's generals, at first appears to serve under him largely to fight a stronger opponent and gets that with Maya. After coming to know her and Asahi, Kilmaria gradually shifts into an anti-heroine role where she knowingly backstabs members of the Demon King's court for Asahi and Maya's sakes.
- Incest-ant Admirer: Maya is completely in love with her brother Asahi and constantly hits on him, who is very disturbed by this.
- Informed Attribute: Despite being considered one of the Demon King's generals, Kilmaria largely tends to either challenge Maya to fights or just hangs out with the two.
- Leeroy Jenkins: In his first adventure, Asahi over-confidently charges into battle without even checking to see if he gained any superpowers or high stats. If Maya had not shown up, he would have gotten himself killed.
- Ms. Fanservice:
- Maya wears a brown tube top, that might as well just be a bra, that exposes her stomach and short shorts.
- Kilmaria wears a Chinese-style dress that exposes her breasts and waist. As such, Maya accuses her of being half-naked.
- Mundane Made Awesome: Episode 6 has a brief scene where Maya and Kilmaria have an epic, tree-leveling battle over the fact that Kilmaria dislikes eating green peppers.
- Only Sane Man: Poor Asahi has to deal with his older sister's unwanted affection and her destructive battles with Kilmaria.
- Pet the Dog: Kilmaria takes a liking to Asahi to the point she develops murderous rage towards Gloria and attempts to intervene in the fight in episode 8.
- The Power of Love: Maya explains her ridiculously high stats as being the result of her complete devotion to Asahi. Whether that's true or not is left ambiguous.
- Running Over the Plot: Asahi gets isekai'd much like a lot of protagonists, only in his case it's Car-kun that sends him to the other world.
- Sitcom Arch-Nemesis: Kilmaria goes from Blood Knight to this, after losing to Maya, fast enough it'll make your head spin.
- Gloria exists to be this towards Asahi after she lost to him.
- Throw the Dog a Bone: After repeatedly losing fights and having to be bailed out by Maya or Kilmaria, Asahi finally wins against Gloria by blinding her with a light spell and then holding his sword against her neck, making her surrender.
- Trapped in Another World: Starts the classic way, with the protagonist getting into an accident and reincarnating into a fantasy world after his apparent death. Then it takes a turn for the wacky when the protagonist's sister figures out what's going on and beats herself into a coma to follow him there, which partially gets subverted in the second ending sequence.
