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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 by Kisetsu Morita (森田季節), with illustrations by Benio. Starting life in 2016 as a Web Novel the series was picked up by SB Creative in 2017 and distributed as a Light Novel. In that same year a manga adaptation was published by Square Enix for their online platform, GanGan Online. The manga is illustrated by Yuusuke Shiba (シバユウスケ). An official English translation of the novel series is produced by Yen Press.

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 Plateu" 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 on the small side, 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.
  • 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.
  • Blob Monster: The slimes.
  • Bi the Way: Halkara
  • 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: Her New Life in Another World Bonus. After all this 300 years, Azusa looks like the "high school girl body" she had when she comes to this world.
  • 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.
  • 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 Hala Magic, a devastating spell that can destroy even Azusa. The problem is, it only works on her, 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.
  • 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.
  • 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.
  • Generation Xerox: 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.
  • Family of Choice: Azusa and her comrades refer to each other as a family.
  • 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, which she had applied for, 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 use it to prepare potions and by extension serves as the village doctor.
  • 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.
  • 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.
  • 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 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.
  • 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.
  • 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.
  • 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).
  • One-Shot Character: The angel that gives Azusa her new life in the new world only appears in the first chapter, and is never heard of nor brought up ever again.
  • 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.
  • Polar Opposite Twins: The slime spirit twins have diametrically opposed personalities, Falfa being hyper and warm, Shalsha being reserved and cold.
  • Promotion to Parent: Falfa and Shalsha consider Azusa to be their mother, 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 all look like young adults or little children for several hundred years.
  • 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, 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 Isekai Slice of Life Now Begins!"
  • Squishy Wizard: Averted, while Azusa has the appearance of a young witch, she packs physical strength as much as her magical power. She is capable of up rooting 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.
  • 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.
  • White Like Me: A Downplayed version. After she dies, Azusa goes from a dark haired Japanese woman in her late twenties to a blond haired, blue eyed, European girl in her teens.
  • 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.
  • 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.
  • 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.

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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