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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 is a Japanese Light Novel series by Kisetsu Morita (森田季節), with illustrations by Benio. Starting life in 2016 as a Web Novel, it 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 due to reprise their roles.


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 Plateau" and all manner of adventurers, dragons, and vengeful spirits come knocking on her door...


This work provides examples of:

  • Accidental Misnaming: To Flatorte's dismay, no one can or is willing to pronounce her name right.
  • A-Cup Angst: About the only thing Azusa dislikes about her new life is that her breasts are smaller than her previous life, and since she is immortal there is no chance of that changing. Somehow, it doesn't occur to her that due to her incredible power, and the ability to create entirely new spells because of it, she could fix this, particularly poignant as age-regressing magic is shown to exist.
  • Affably Evil: The King of the Demons, Pecora, is polite, gentle, and kind towards allies and equals, like Azusa. She is also mischievous, cunning, and outright evil, like the time she had Azusa unknowingly enslave Flatorte (the leader of the Blue Dragons) by asking Azusa to pet her horns—an act the dragons consider to be a sign of complete and utter surrender and subservience to another.
  • The Alcoholic: Halkara is frequently drunk and getting into trouble, or otherwise is of absolutely no use to anyone.
  • Alien Catnip: Halkara's famous energy drinks, Nutri-Spirits, have the opposite effect on demons, acting more like very strong alcohol. Beelzebub is a particularly big fan of them, though she accidentally caused Halkara (and by association, Azusa) no shortage of misery before they were made aware of this fact.
  • 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.
  • 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.
  • Beware the Nice Ones: Azusa. She may ideally want to solve her problems as peacefully, diplomatically, and with the least amount of violence and catastrophically powerful magic possible, but she won't hesitate to use the full extent of her power if needed.
  • Born as an Adult: Keep in mind Azusa reached this world through reincarnation. She appeared in an adult body and had no known parents.
  • Butt-Monkey: Halkara seems to exist solely to suffer in comedic fashion, cause trouble to Azusa and the others, and suffer even more as a result. Her lack of tact and sensibility, her alcoholism, and generally impulsive nature only make it worse.
  • Child Prodigy: Falfa and Shalsha are chronologically 50 years old, but look, act, and have the emotional maturity of small children. This does not stop them from being incredibly smart, with high level academic knowledge on various subjects like math and history, along with adult-level reading comprehension.
  • 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.
  • Complete Immortality: Asuza's New Life in Another World Bonus. After 300 years, Azusa still has the "high school girl body" she had when she came to this world. She specifically asked for The Ageless but seems to have become completely immortal with Nigh-Invulnerability coming from centuries of levelling up.
  • Cool Big Sis: Azusa refers to Beelzebub as this, when thinking about what traditional family roles members of her Family of Choice fit into. Pecora also treats Azusa like this and coerces her into filling the role using her authority as the Demon King. Rosalie also treats Azusa like this in their Family of Choice.
  • 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.
  • Crippling Overspecialization: Shalsha learns Smiting Evil Magic, a devastating spell that can destroy even Azusa. The problem is, Shalsha's version of the spell only works on Azusa, and she hasn't had the time nor the capability to learn anything else. It also requires a lot of built up mana, so after using it once it would require years if not decades to be used again.
  • Curb-Stomp Battle: Because Azusa is the most powerful an immortal witch can possibly be, anyone and anything that tries to challenge her immediately faces this. Laika also gets her moment when she defeats Shalsha with no effort whatsoever.
  • Cute Ghost Girl:
    • Rosalie, who haunted the site of Halkara's second energy drink factory in Nascute, and ended up becoming a new member of Azusa's family.
    • Falfa and Shalsha are slime spirits born from the souls of slimes Azusa had killed for 250 years.
  • Cute Slime Mook: The slimes, which are exported from Dragon Quest, the codifier of that trope.
  • Cute Witch: Azusa herself.
  • Defeat Means Friendship: 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.
  • 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.
  • Driven to Suicide: Rosalie's backstory. She was the daughter of a nobleman, who tried to sell her as a prostitute when his business began to fail. He lied to her and claimed she was being married off to a rich man, and when she found out, decided to hang herself.
  • Elegant Gothic Lolita: Laika prefers this style of clothing in her human form.
  • Family of Choice: Azusa and her comrades refer to each other as a family.
  • Generation Xerox: Downplayed. Natalie, the receptionist for the adventurer's guild in Flatta, looks exactly the same as her 300-or-so-years-old ancestor of the same name and appearance. It's averted in the manga, where they share the same name and profession, but not the same appearance.
  • 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.
  • Involuntary Transformation: Falfa ends up mysteriously stuck in her blob monster slime form during one arc.
  • 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.
  • Know Your Vines: Azusa's first skill after reincarnation; she uses it to prepare potions and by extension serves as the village doctor.
  • Level Grinding: Taken Up to Eleven. Azusa spent 300 years accidentally grinding slimes, every single day, getting to max level thanks to an experience compounding phenomenon when enough of a certain type of monster is killed.
  • 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 .
  • 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.
  • Mayfly–December Romance: Defied. Romance is the one thing Azusa continues to forego post-reincarnation, because she wants to prevent any heartbreaks that come with this. (Though her new family has a number of long-lived girls, she declares she doesn't swing that way.)
  • Meaningful Rename: Azusa rewrites her name in Katakana upon reincarnating, to dissociate from her old life.
  • 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.
  • Meido: Laika's normal outfit in her humanoid form evokes this, with its design and her subservient behaviour towards Azusa as her disciple. During one of Flatta village's festivals, the entire main cast dress up as them, and run a maid cafe.
  • Merger of Souls: Falfa and Shalsha are merged from the souls of the slimes Azusa killed over the centuries.
  • Mundane Utility: Upon learning that she can summon a frost so powerful it instantly freezes a small spring, and the waterfall and river it is fed from, Azusa starts cooling and preserving her meals without the need for modern refrigeration technology.
  • 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.
  • My God, What Have I Done?: Azusa, without quite understanding the cultural significance of it, touches Flatorte's horns thinking it will help foster peace between the Red and Blue Dragons. What she didn't realize was just how completely Blue Dragons become subservient to their mistress or master, never leaving their side and not even eating or sleeping unless specifically ordered to, and if they should leave their mistress/master's side for any reason, even being ordered to, the dragon will commit suicide. Azusa is pretty understandably freaked out and compares it to actual slavery.
  • Naked Apron: Halkara wears this when preparing medicine, since Bunsen burners heat up the surrounding air.
  • New Life in Another World Bonus: The premise of the LN and manga. The protagonist worked herself to death as an Office Lady and was granted her wish of immortal youth as a witch in a standard RPG-Mechanics Verse. The overpowered aspect comes from the fact that she killed about 20 slimes every day for three hundred years and thus reached the maximum level without ever realizing it (because she never had to fight anything tougher than a slime).
  • Office Lady: Azusa's previous occupation.
  • Our Demons Are Different: Save for territorial disputes, they are not that different from humans, having an established government with taxes, infrastructure and government services with offices and secretaries to run them, and nutritional needs similar to other creatures—no feasting on souls here. They all tend to just have magic, be particularly long-lived and youthful, and have animal like features like goat horns.
    • Applies to their naming system too. Beelzebub is simply named after a famous demon of the past. She originally was the simple daughter of countryside greengrocers and felt she could never live up to her famous name until she got appointed Minister of Agriculture
  • 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.
  • Phenotype Stereotype: Azusa became a fair-skinned, blue-eyed blonde witch in a Medieval European Fantasy universe after reincarnation.
  • Polar Opposite Twins: The slime spirit twins have diametrically opposed personalities, Falfa being hyper and warm, Shalsha being reserved and cold. In addition, Falfa is a prodigy in mathematics while Shalsha is a prodigy in history.
  • Promotion to Parent: Falfa and Shalsha consider Azusa to be their mother, since while she did not birth them or have direct involvement with their creation, it was because of her that they were created.
  • Really 700 Years Old: Azusa, who is at least 300 years old but still looks 17, along with most every other non-human character such as the dragons, the demons, and the slime spirits, who've all looked like young adults or little children for several decades or centuries.
  • Red Baron: Azusa is known as Witch of the Highlands long before she is found to have maxed out her level, because she is Completely Immortal and she has been a competent herbalist over her centuries of life.
  • 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.
  • 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.
  • 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've Been a Civil Servant for 1,500 Years and Became a Minister After Bending to the Demon King: A manga about Beelzebub's backstory.
    • The Elf's Dinner: A web novel about Halkara's backstory.
    • The Red Dragon Women's Academy: A web novel about Laika's backstory.
  • Squishy Wizard: Subverted; while Azusa has the appearance of a young witch, and she technically has the stat spread of a Squishy Wizard, with defense as her lowest stat, her obscene level means that her combat-oriented stats are still incredibly high, just in the 400s-500s instead of 800s-900s like her more magic-oriented stats. She is capable of uprooting trees and tossing full grown dragons around like they were toys, and is capable of doing so for long, sustained fights such as the disastrous Red Dragon Wedding.
  • Third-Person Person: Falfa and Shalsha refer to themselves in the third person. This is one of their childish traits.
  • 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.
  • Tragic Dream: Azusa dreamed of traveling to Switzerland, then her company worked her to death.
  • Translator Microbes: As part of her reincarnation, Azusa is capable of understanding, speaking, reading, and writing the language of Flatta. Especially helpful since she spends quite a lot of her first 300 years reading botany books and becoming an herbalist.
  • Trauma Button: Because Azusa died in her former life through karoshi, the idea of working beyond one's means triggers flashbacks.
  • 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.
  • White Like Me: A Downplayed version. After she dies, Azusa goes from a dark haired Japanese woman in her late twenties to a blonde haired, blue eyed, Caucasian girl in her teens.
  • Wizards Live Longer: The woman at the guild reception says that some powerful witches can fine tune their mana circulation to prolong their lives but is shocked that Azusa has immortality at level 1.
  • The Workaholic:
    • Azusa in her former life was completely devoted to her job, and never had time for any sort of life outside of it. After working 50 straight days with no break she collapsed and died. The trauma of it was so severe that she snaps at Laika and insists that she take breaks, and work reasonable (human) hours, in spite of Laika's insistence that as a dragon she can perform far harder work for much longer before tiring.
    • Beelzebub caused a misunderstanding among the demons regarding Nutri-Spirits because of this—she fell sick due to overworking after drinking Nutri-Spirits, and the other demons mistakenly thought it was Nutri-Spirits that was harmful.

Alt. Title: 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 (Suraimu Taoshite Sanbyaku-nen, Shiranai Uchi ni Reberu Makkusu ni Nattemashita)

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