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Light Novel / I've Been Killing Slimes for 300 Years and Maxed Out My Level

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The Witch of the Highlands, Azusa, surrounded by her apprentices and "children"

I've Been Killing Slimes for 300 Years and Maxed Out My Level (スライム倒して300年、知らないうちにレベルMAXになってました, or Suraimu Taoshite Sanbyaku-nen, Shiranai Uchi ni Reberu Makkusu ni Nattemashita) is a Japanese Light Novel series by Kisetsu Morita (森田季節), with illustrations by Benio.

The series tells the story of Azusa Aizawa, a regular Japanese salarywoman who finds herself dying from overwork at age 27. A merciful goddess takes pity on her, and offers her a new life in another world, where she's free to live the simple, carefree, and easy life Azusa has always wanted. She takes the offer, and finds herself an immortal witch in a medieval fantasy world.

Azusa proceeds to enjoy her new life for the next 300 years, laying around and relaxing, becoming an herbalist and medicine woman for the nearby village of Flatta, and making some money on the side by killing the slimes and selling their cores at the guild. Trouble starts when she takes a power assessment on a whim, and she and the receptionist Natalie discover that Azusa has become max level, with the highest stats possible, and access to a number of incredibly powerful spells and abilities beside. In spite of Azusa's efforts to keep it secret, word spreads of the all-powerful "Witch of the Highlands" and all manner of adventurers, dragons, and vengeful spirits come knocking on her door...


Starting life in 2016 as a Web Novel, the series was picked up by SB Creative in 2017 and distributed as a Light Novel series; beginning with Volume 5 in 2018, some of the novels have had special editions which come with Drama CDs. The same year the light novels began, a manga adaptation was published by Square Enix for their online platform, GanGan Online, illustrated by Yuusuke Shiba (シバユウスケ). Official English translations of the novels and manga are produced by Yen Press, though the novels don't come with the Drama CDs. An anime adaptation of the novels was announced in 2019, with the cast of the Drama CDs reprising their roles, and began airing in April 2021.

You can view the first Japanese anime trailer here.


This work provides examples of:

  • Achievements in Ignorance:
    • A major part of the story premise is that Azusa was simply going about her new immortal life killing 20-25 slimes a day in exchange for money. She did this for 300 years, completely oblivious to the fact she was Level Grinding by doing so, until one day she randomly decided to check her stats and found out she maxed her level.
    • Shortly into the story we learn that in her mindless slaughter of countless slimes over the centuries, Azusa wound up unintentionally "creating" the slime spirits Falfa and Shalsha.
  • Actor Allusion: In the anime, Goodly Godly Godness, the Goddess that reincarnated Azusa, who states she will look "17 years old, just the way I like it", is voiced by "eternally 17" Kikuko Inoue.
  • An Aesop: The show (and the novels beforehand) constantly harp on slowing down and making a work-life balance, leaning in hard against Japan's overwork culture. This moral is central to Azusa's very character and her relationship to the other characters, so it works where a more subtle moral would not.
  • All-Natural Snake Oil: Downplayed. Unlike Azusa, who prepares medicine for acute diseases, Halkara mainly prepares what Azusa compares to "nutritional supplements"—things that don't really treat any disease, but do help in maintaining general health.
  • All Part of the Show: When Kuku finishes her performance at Flatta, she lies back, and both Azusa and Flatorte think it's part of the choreography. It is after moments of Visible Silence that they realize Kuku fell unconscious.
  • And I Must Scream: Falfa is transformed into a slime at one point. Later, after her recovery, it turns out they were sentient and aware the whole time, but unable to communicate with anyone or anything as they were trapped in slime form.
  • Asskicking Equals Authority: The Demons and both the Red and Blue Dragon factions all follow a "Might Makes Right" philosophy, their absolute leaders being the most fearsome of them all.
  • Back for the Finale: Episode 12 of the first season has all of the major named characters with a connection to the main cast show up to help with the maid cafe, including the demons Beelzebub, Pecora, Vania, and Fatla, Fightie the slime, Eno the witch, and Kuku the almiraj. Meanwhile, several of the more notable secondary characters show up amidst the customers, such as guild receptionist Natalie, the loose-lipped guy who spread the info of Azusa being a max-level witch, the adventuring party who first fought her and truly exposed her incredible power to the world, and the masochistic guy trio. Even the titular slimes get an appearance being killed by Azusa and Laika, after having been sidelined due to so many events taking place far away from their spawning fields.
  • Bland-Name Product: In the anime, Nutri-spirits' label looks a lot like the Japanese energy drink Lipovitan.
  • Casual Kink: To the surprise and discomfort of Azusa and Laika, in a town west of Flatta there's a "public" bar called "A Pig Would Be Far More Useful Than You", which as implied by the name is dedicated entirely to appealing for masochistic customers, with the waitresses being as insulting and demeaning as possible when taking orders and serving food. Everybody there views this as a completely normal thing and the bar otherwise works like normal ones, though the main waitress expresses understanding for how outsiders that don't know the gimmick might find it weird.
  • Colour-Coded for Your Convenience: Slimes with a pale coloring are evil, while the ones with darker hues are good. The two main factions of dragons are also either exclusively coloured Red or Blue.
  • Corrupt Bureaucrat: Governor Golder of Nascute. Everyone knows he's lazy and useless until someone tries to operate a business without bribing him, or otherwise threatens his cushy position and all the power and money it affords him.
  • "Could Have Avoided This!" Plot: Azusa's search for a cure to the gnome mushroom's effects is one of these on multiple levels. When she asks the demons for information, Pecora points her towards Yggdrasil, which she spends a sizable amount of time (and money) climbing. When she finally makes it to the pharmacy at the top, she discovers that the cure is Eno's Mandragora Pills. The thing is that 1) Azusa is good friends with Eno and could have just asked her, 2) she still has a bottle of the pills at home, 3) it turns out that while dragons can't fly up the tree, smaller sized wyverns can, as proven by Eno showing up to drop off a shipment at the pharmacy, and 4) Eno also ships to Vanzeld Castle and Pecora definitely knew already, all of which means that she wasted all her time climbing a giant tourist trap tree for a solution she already had at home.
  • Cover Innocent Eyes and Ears: In the manga and anime, whenever a perverted image is within eyesight of Falfa and Shalsha, their eyes tend to get shielded by a responsible adult.
  • Curb-Stomp Battle:
    • Because Azusa is the most powerful an immortal witch can possibly be, almost anyone and anything that tries to challenge her immediately faces crushing defeat.
    • Shalsha manages to give Azusa herself one, courtesy of a Kryptonite Factor.
    • Laika also gets her moment when she defeats Shalsha with no effort whatsoever.
  • Cute Slime Mook: The slimes, which are exported from Dragon Quest, the codifier of that trope, are numerous enough in the fields around Flatta that Azusa can kill 25 of them, every day, without their numbers decreasing. They are the weakest kinds of monsters, providing only 2 EXP each.
  • Defeat Means Friendship: With the exception of Halkara, all of Azusa's incredibly powerful allies or adoptive family members were once her sworn enemies, until she soundly beat the crap out of them, or otherwise outsmarted them.
  • Didn't Think This Through: After Azusa finally gets the cure for the Gnome-Maker Mushroom which shrunk her, she eats them in Pecora's throne room to proudly grow back to normal in front of the others. And she's not suspicious on why Pecora is also encouraging that. Shalsha realizes that her child sized clothes won't fit her anymore.
  • "Do It Yourself" Theme Tune: The opening theme is sung by Aoi Yūki (Azusa), while the ending theme is sung by Azumi Waki (Flatorte).
  • Dragon Hoard: Laika mentions this is a racial trait among the dragons, which is why she did not need much time to pay Azusa back for destroying the latter's house.
  • Early-Bird Cameo: In the manga, while people are gathered around Eno and Azusa is exposing her as the fake Highland Witch, someone in the crowd keeps saying if Eno could be an undead to the irritation of the others, even getting Azusa's attention for a second. After Eno's story ends in the next chapter, we see a Cat Girl in her room being upset that Eno wasn't an undead and that she is still alone. Her cat ears were also visible on one of the silhouettes of the crowd. Her situation gets followed up in the next story.
  • Fantastic Aesop: The aesop of the series is that overexertion and working too hard can cause you more harm than good, no matter what your job or superiors desire. However, the way the protagonist overcomes this problem is by being reborn as an immortal witch. Many characters join up with her in order to learn how to be as powerful or successful as she is, and they're all immortal and/or Long-Lived themselves and thus can afford to imitate her methods without the constraints of a normal human lifespan. Likewise, things like Levels that build stats don't exist in Real Life; people cannot gain immense physical power from, say, swatting 25 flies every day. This does not diminish the lesson the story is going for in any way, although its solutions cannot be easily translated into the real world.
  • The Force Is Strong with This One: A sufficiently trained magic user is capable of sensing the Mana a person possesses, and thus gauging their magical power. It's for this reason that Azusa's efforts to avoid showing her power and become famous fail, because her first opponents, a group of adventurers looking to test their mettle, have a mage who can sense the massive amount of mana that's gushing from her body.
  • Fountain of Youth: Azusa's body has regressed to that as a child quite a few times in the light novel (the anime covering the first time it happened, which was the result of her eating a gnome mushroom), with Laika, Flatorte and Beelzebub joining her one time.
  • Gale-Force Sound: When Kuku's very loud heavy metal music is first introduced, Rosalie gets blown away into the sky.
  • Geometric Magic: Magic circles aren't necessary for spellcasting, but can be drawn on the ground to make long-lasting effects more reliable to cast. Azusa uses a large hexagram-and-rune formation to create a major Protective Charm, while demons sometimes print them on paper to store single-use telecommunication spells.
  • Ghibli Hills: We are told how scenic Nanterre and Azusa's highlands are in the light novels and this is shown in the anime adaption. The backdrops and landscapes are sumptuously drawn, detailed, and made to look beautiful and impressive.
  • Gratuitous English: In Japan, the series has the English tagline She continued destroy slime for 300 years. Yen Press render it as She slaughtered slimes for 300 years instead.
  • Great Gazoo: Goodly Godly Godness, the very being who reincarnated Azusa. She is later exiled to Azusa's world and causes no end of trouble for Azusa and family. Even more amusing in that the first couple of volumes of the Manga show Azusa having fond thoughts and memories about the "angel girl" who reincarnated her not knowing the later trouble she would get from the goddess.
  • Great Offscreen War: It's been 500 years since the Demon-Human wars in Azusa's world. The last Demon King before Pecora created the truce himself and, although as shown in Beelzebub's backstory, there are still violent factions among the demons, most of the demons of Azusa's world are peaceful now. This is good since the Demons here are shown to be magically and technologically far in advance of the humans (gets turned up to 11 after Pecora gets technology from the remains of Thursa Thursa creating games with battle dolls and phantasm streaming). Because the Demons have remained hidden after the war, most humans have only shadowy and incorrect information about them, not even being able to recognize them as demons when they see them.
  • Identical Panel Gag: This happens as Flatorte's clothes and underwear get taken by boars and dropped into the river.
  • Improbably Female Cast: All the main characters are female, and a good majority of the secondary cast is female too, despite it being quite clear that there are a decent number of males amidst the minor and background casts.
  • Incredible Shrinking Man: At one point, Azusa inadvertently eats some mushrooms that make her shrink to child size, courtesy of Halkara, and everyone around her treats her like a kid.
  • Kangaroo Court: Azusa and co. end up being subjected to this by a corrupt official from a neighbouring village, Governor Golder of Nascute. The phony claim is that Halkara has been producing and selling medicine (her Nutri-Spirits) there without a license; she had applied for one, but did not send along an accompanying bribe to the governor to "speed up" the process.
  • Kill It Through Its Stomach: Discussed while fighting the giant serpents in the World Tree. Even though Azusa has shrunk, she's confident she can defeat them from the inside even if she gets eaten. But the leviathan sisters throw her to safety. Pointing out that it's going to be a bloody mess. Especially since these are innocent wild animals, not monsters.
  • Leaning on the Fourth Wall: Early on in Beelzebub's spinoff, Pecora mentioned Beelzebub's long tenure as a bottom-tier bureaucrat is like "trying to be the strongest by killing nothing but slimes", or, otherwise, what Azusa accidentally did in the main story.
  • Long Title: Twelve words, if you write "Three Hundred" numerically. What's more, the English title is already shortened; a literal translation would have "Without Knowing It" added to the end.
  • Lost in Translation: Azusa's Meaningful Rename would puzzle most English readers as to why that would count as a rename. But to any Japanese it is a rename, with a connotation that she no longer sees herself as Japanesenote . The anime adaptation, which includes spoken dialogue and has at least a little intention of being presentable to English-speaking audiences, eases this a bit by also having her flip the given name-surname order, going from Aizawa Azusa to Azusa Aizawa. The full meaning behind the rename is still lost, but English viewers at least can comprehend there being a change at all. Meanwhile, in the dub this entire translation debacle is thrown completely out the window, with Azusa instead declaring "Goodbye, Azusa Workaholic, and hello, Azusa lazy witch."
  • Male Gaze: Halkara's introductory segment in Episode 3 has the camera aiming at the more... curvy parts of her body, firmly establishing her as a Ms. Fanservice. Different points in the episode continue showing off her "assets", solidifying her status.
  • Mana: A key element of the story, and how much you can store and use at any given time is a measure of your power as a witch, a demon, or a dragon. Azusa actually tries to pass herself off as much, much weaker than she really is, but a trained mage can easily see the overwhelming aura of power she radiates at all times.
  • Meaningful Background Event: During Halkara's story introduction, each scene taking place in Azusa's house has a single random fly periodically buzz around. Near the end of her introduction, it turns out that said fly was a shapeshifted Beelzebub, the person Halkara was running away from.
  • Medieval European Fantasy: The series has all the usual trappings of it, with elves, demons, and dragons, and Azusa's home and Flatta are explicitly stated to have European-esque designs and trappings.
  • Medieval Stasis: The world doesn't seem to change in the 300 years after Asuza's arrival. Granted we don't see outside the village until after the Time Skip, and she does live in the highlands. Rural places don't change as quickly as more urban places. However, episode one of the anime does show that the guildhall was redesigned and given a second floor sometime before Azuza arrives to discover she maxed out her level capacity, so there's at least a downplaying through implication of improving construction methods throughout the centuries.
  • Mundane Utility:
    • After 300 years of accidental level grinding, Azusa discovers she has gained ice magic so powerful it can flash freeze a small spring and the river feeding it. After that, she mostly uses it to preserve her food without modern refrigeration technology.
    • Laika uses her fire breath to flash-cook omelettes while shapeshifted into a human. Despite Azusa's own long experience with magic, she's a bit thrown to see it the first time.
  • Muscles Are Meaningless: One's stats in the RPG-Mechanics Verse can be completely unrelated to one's physical body. As a top-level Witch, Azusa has the body of a petite seventeen-year-old girl, but can still swing around a full-grown dragon by the tail.
  • Musical Episode: Episode 10 is basically an excuse to have the entire cast show their singing skills.
  • Must Have Caffeine: When Halkara mentions she makes Nutri-Spirits, a popular energy drink, Azusa finds it eerily similar to the kind of thing she drank a lot in her past life. Beelzebub really likes it, as do many other demons.
  • Only I Can Kill Him: Hugely downplayed but present between Beelzebub and Azusa. Beelzebub is the only one who can come anywhere close to matching Azusa in a fight. In their second match, Beelzebub is able to block Azusa's punches (at great painful cost) much to Azusa's surprise and not get one punched from the start. In a later adventure when Azusa goes berserk because of a magically induced food craving, she easily dispatches the entire Demon army but Beelzebub is able to grapple her and hold her in place long enough for Fatla to feed Azusa what she's been craving and calm her down.
  • Our Ghosts Are Different: Earthbound spirits are usually stuck in the place they died. They can be purified by the Church, or destroyed by demons. Rosalie's permanently intangible, and displays invisibility, possession, and telekinesis.
  • Protective Charm: Azusa improvises a powerful barrier to ward the nearby village against monsters and other hostile forces that might be drawn to her. The spell itself is undetectable, but it traps a would-be thief in magical bindings when he tries to act.
  • Releasing from the Promise: Defied. Azusa tries to release Flatorte from serving her by ordering her to be free... only to have Flatorte point out that freedom contradicts the meaning of orders, and subsequently manage the contradiction by identifying herself as both obedient and free.
  • RPG-Mechanics Verse: While not being based on a videogame, so far as has been revealed, the powers of an individual are determined by numerical figures like "levels" and "stats." Human adventurers use special magical tools found at any adventurer's guild branch.
  • Running Gag: In the manga, one of the end of volume omakes will be about someone drawing a silly representation of how they perceive Azusa's magic power. It gets sillier with each iteration, going from depicting the energy streaming out of Azusa to depicting food as somehow representing her power leakage.
  • Saying Sound Effects Out Loud: While not directly spoken by the characters, any time a situation calls for a notable sound effect in the anime (like heart-beating or wing-flapping), rather than proper sounds, the voice actors provide echoing readings of the scripted noises. This also includes the occasional Unsound Effect like "flail" for whirling one's arms around wildy.
  • Self-Fulfilling Prophecy: The Azusa clan spend most of their time in the Demon Capital worrying so much about offending the demons, with them especially making frantic efforts to prevent Halkara from getting herself executed out of her idiotic clumsiness, that when they have an audience with the Demon King their nervousness ends up with Halkara accidentally knocking the king unconscious, resulting in her being slated for execution due to harming royalty out of idiotic clumsiness.
  • Shapeshifter Baggage: Dragons and leviathans can both use magic to take on smaller human forms. Azusa lampshades this when she finds out about the latter.
  • She Is the King: The King of Demons is a traditional title, and does not change for the gender of the one currently holding it. As of volume 2, it is held by Provato Pecora Ariés.
  • Shout-Out: When demonstrating the weak point of evil slimes, Falfa does so while saying "Omae wa mo shindeiru".
  • Slice of Life: In spite of all the conflict and fights Azusa gets into, the majority of them end up being Curb-Stomp Battles to make more time for cute antics with her ever-growing number of students and adoptive family members. This is even noted by the publisher; the poster above has the headline "The Slow Life in Isekai Now Begins!"
  • Spinoff: Three as of February 2020, all of which are backstories of Azusa's family members:
    • I Was a Bottom-Tier Bureaucrat for 1,500 Years, and the Demon King Made Me a Minister: A web novel about Beelzebub's backstory, with a manga adaptation.
    • The Elf's Dinner: A web novel about Halkara's backstory.
    • The Red Dragon Women's Academy: A web novel about Laika's backstory.
  • Standard Japanese Fantasy Setting: This trope is baked right into the DNA of the premise; the protagonist maxed out her level over the course of 300 years by killing Cute Slime Mooks. Her Family of Choice is comprised of a number of Cute Monster Girls ranging from slime spirits to a dragoness to a cute poltergeist to an elf, and a demoness as a Cool Big Sis. She finds out that she's reached max level via a nearby Adventure Guild, and mazoku (translated as "demons" in English) have their own society filled with a diverse assortment including ogres, trolls, animal-themed Beast Men, and so on. There are also gods and other deities, such as the one who reincarnated the protagonist and made her immortal in the first place.
  • Starving Artist: According to Flatorte, this is a chronic problem among minstrels, as their income usually cannot cover basic living costs and requires doing odd jobs to survive.
  • Take That!: Azusa is a victim of Karoshi (Death by Overwork). In Japan, this is an especially serious problem, since Japan’s corporate work culture emphasizes loyalty to one’s employer, encouraging a willingness to give up time at home with family, and work insane hours, leading to a large number of people dying or committing suicide due to the incredible pressure such a lifestyle brings with it. Because of this, after reincarnating, Azusa has absolutely no love for that lifestyle, and will not hesitate to shut down her family members if they ever say or imply that they might start overexerting themselves.
  • Tempting Fate: Happens regularly. Most of the main characters are introduced through this.
    • In the slower paced LN, after Azusa defeated the adventurers she spends time studying about monsters to give people advice on how to combat strong creatures like Dragons, instead of fighting them herself. While also hoping her rumors would stop spreading among people. It’s at this point Laika the dragon knocks on her door.
    • With Laika's suggestion, Azusa creates a magic barrier to protect the village. But they can't actually verify it's working until someone with ill intent comes. Azusa is optimistic that nothing will happen. They capture a minor criminal that night.
    • Azusa is teaching Laika that slimes are a good source of steady experience and income. Especially since they could never take revenge. Cue the introduction of Shalsha the slime spirit coming to kill her.
    • Azusa says it's great to have a dragon as a disciple as it discourages adventurers from visiting her for a challenge. While mid-sentence of hoping the peace continues, there's a knock on the door: Falfa arriving to warn her about her sister Shalsha.
    • After the slime sisters became a part of the family too, Laika wonders who could join them next: An elf? A demon? The next visitor is the elven alchemist Halkara being chased by Beelzebub, a demon.
    • During the party before Laika's sister's wedding, her father is optimistic that the blue dragons won't disturb them like they always do. They, including Flatorte, of course, arrive very soon.
    • Halkara found a place to build a new workshop bigger than ever. Meanwhile, people living at that area think it also won't be lasting long. Later Azusa warns her about overworking and she agrees that it'd be bad to become a ghost while working. Next panel, she's terrified about the encounter she had with the ghost Rosalie.
  • This Is Gonna Suck: As most threats to Azusa can't actually harm her, overpowered as she is, most of her worrying is about not delivering too dramatic of a Curb-Stomp Battle, and having yet more powerful threats literally knocking on her front door.
  • Trail of Bread Crumbs: In the anime, Beezlebub attempts to do this to avoid getting lost when the gang heads to the Demon King's Castle to find the Intelligent Slime. Unfortunately, slime-form Falfa ends up eating all the crumbs that are dropped.
  • Twinkle in the Sky: In the anime, Azusa spins Halkura around rapidly then tosses her in an attempt to get Rosalie out of her body. When Azusa throws her, Halkura quickly becomes a twinkle in the sky. It doesn't get Rosalie out, by the way.
  • Voluntary Shapeshifting: Demons and dragons have the capability to switch between their more monstrous (and oftentimes, much more massive) forms, and humanoid shapes with clothes included.
  • What Happened to the Mouse?: In the first volume there is a long and in-depth description of Falfa and Shalsha's hair. Their hair is actually slime tentacles that they can freely control, something like Squid Girl. However, after this discussion, this talent is never used, mentioned, or brought up again. None of the other intelligent slimes that Azusa and the gang encounter are shown to have or use slime tentacles.
  • Weredragon: Thanks to their high natural mana, dragons can transform at will into a set human form, albeit one with horns and sometimes a tail. They use this for convenience when traveling among humans and also for events like formal banquets.
  • Wizards Live Longer: Past-Natalie noted that some powerful witches can fine-tune their mana circulation to prolong their lives, but is shocked to see from her stats that Azusa has immortality right from level 1.
  • Work Com: Beelzehub's spinoff is partly this as it involves her daily life as the minister.


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