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

I've Been Killing Slimes for 300 Years and Maxed Out My Level is a Japanese isekai light novel series written by Kisetsu Morita and illustrated by Benio. It was serialized online since 2016 on the user-generated novel publishing website Shōsetsuka ni Narō and, in the following year, it was acquired by SB Creative, who published the first light novel volume in 2017. The light novel has been licensed in North America by Yen Press, who published the first volume in April 2018. It has received a manga adaptation by Yūsuke Shiba in the same year as its debut of the light novel in Square Enix's Gangan Online website, also licensed by Yen Press. An anime television series adaptation by Revoroot aired from April to June 2021. A second season by Teddy aired from April to June 2025. The series has also spawned various spin-off novels.

Plot
After living a painful life as an office worker on Earth, Azusa ends up dying from overworking. She finds herself reincarnated as an undying, unaging witch in a new world by a goddess, and now she vows to spend her days as pleasantly and stress-free as possible. She makes a living by hunting slimes, the easiest targets. But after three centuries of doing this simple job, she has become extremely powerful and finds that she can no longer maintain her low-key lifestyle. In time, she gains an adoptive family and becomes friends with many female beings. ==Characters==
Characters
; : :A former Japanese office worker reincarnated as an immortal witch, called . After slaying millions of slimes for over 300 years, she became a level 99 fighter. Wary of any overwork and excitement following her untimely death, she strives for an easy existence, but once word gets out about her unprecedented prowess, she finds herself beleaguered by challengers trying to prove themselves against her, and all sorts of people willing to join her. However, she is compassionate and in time becomes very protective of her adoptive family and friends, much to the chagrin of anyone who deliberately endangers them. She soon receives an upgrade that enables her to match the power of a god. ; : :A roughly 300-year-old shape-shifting red dragon girl. Originally arrogant, she came to Azusa to fight her and prove herself to be stronger than her. After getting soundly beaten by Azusa, she joins her as her first apprentice and housekeeper, eventually becoming her adoptive younger sister. She has a rivalry with Flatorte. ; : :An about 50-year-old slime spirit girl, and the elder of twin sisters. She is one of Azusa's adoptive daughters. Both she and her sister Shalsha are reincarnations of the slime creatures that Azusa killed for a living; but while Shalsha is initially deeply resentful towards Azusa at first, Falfa adores her and considers her their "mother". ; : :Falfa's younger slime spirit twin sister. She is one of Azusa's adoptive daughters. Driven by feelings of revenge against Azusa for killing all the slimes, she learned a type of magic which is effective against one specific race only, but in turn is potent enough to counter even Azusa's magic; she is also very learned in magic lore. After being very easily beaten by Laika, Shalsha and Falfa join Azusa's household upon her invitation. In turn, she abandoned her desire for revenge upon learning that Azusa is not the only one targeting slimes. She is very inquisitive, and habitually takes notes of anything new she comes across. ; : :A young (about 225-year-old) female elf apothecary woman from Frant Province with very abrupt mood swings and a voluptuous build. She invented an extremely popular, alcohol-based energy drink; but when the demon lord Beelzebub drank from it, she became sick (from overworking after getting addicted to it) and then went after Halkara, whereupon the elf, believing that Beelzebub wanted in fact revenge, fled to Azusa for protection. After being given shelter, and after the misunderstanding with Beelzebub is cleared, Halkara decides to stay with Azusa and restart the production of her energy drink. She is very knowledgable about mushrooms, but scatterbrained and accident-prone. She has a rivalry with Eno due to their habits of stealing each other's ideas. ; : :An about 3,000-year-old high-ranking female demon, the Agriculture Minister of the Demon Realm, and Lord of the Flies. Chasing after Halkara after getting addicted to her energy drink (so that its production could be re-started) she challenges Azusa to a fight, but collapses from exhaustion and is nursed back to health by her and Halkara. After the misunderstanding was cleared, she leaves peacefully, but vows to come back to settle her score with Azusa (which she will soon ultimately lose) and get more of Halkara's drink, although she begins to settle in with Azusa's family as her adoptive older sister, but does not really live with her. She also treats Falfa and Shalsha as if they are her daughters. ; : :An over 400-year-old blue dragon girl who first meets Azusa and her extended family while she and her flock attempt to disrupt the wedding of Laika's older sister, out of simple jealousy that her blunt demeanor drove away her own fiance. After Azusa single-handedly thrashes the aggressors, and a final act of aggression is stalled by Beelzebub, she is forced to sign a peace treaty between the red and blue dragons. Afterwards, as part of her peace obligations, she also (much to Laika's disgust, which results in them becoming rivals) joins Azusa's troupe—the only alternative being to commit suicide due to her culture. ; : :A ghost girl who died about 200 years previously at the age of 15. The daughter of a merchant who had fallen on hard times, she committed suicide after learning that her father wanted to sell her off as a prostitute. Her restless ghost began haunting the merchant's estate, which later became the site for Halkara's new energy drink factory. After being caught by Azusa, Halkara and Beelzebub, she is, with some effort, relocated to Azusa's house and joins her adoptive family. She is good friends with Muu. ; : :A leviathan woman, Beelzebub's secretary, and Vania's older sister. She and Vania are both shapeshifters, able to assume the form of a gigantic, flying whale. Despite the myth that leviathans are water creatures, they are actually air dwellers, and are usually employed as living transportation (complete with a resort hotel on their backs) by demons, devils and their privileged guests. To fulfill this obligation, both sisters work in tandem: while one does the transport, the other uses the hotel facilities (especially the bath) to relax. ; : :A leviathan woman, Beelzebub's assistant secretary, and Fatla's younger sister. ; : :An over 1,000-year-old demon girl and the "King" of the Demon Realm from its capital city Vanzeld. Despite her awe-inspiring title, her natural form is a cute, petite girl with ram horns and three tails, and she is, most of the time, surprisingly cheerful and informal. She has also a submission complex; after being accidentally knocked out by Halkara, and with Azusa beating her in a duel over Halkara's life, she gladly submits to her "conqueror". She now considers herself to be Azusa's younger sister and is very obsessive with her. She later forms an alliance with Muu. ; :In manga: :In anime: :A normal slime which is completely black. :Smarsly (in manga) / Intellie (in anime) is name given to it by Azusa. (Shortened name is used in light novel volume 12 and later.) ; :In anime: : :Sandra is a mandragora girl over 300 years old, capable of burrowing swiftly through the ground. Initially fearful of witches, who sought to use her for medicinal purposes, she eventually trusts Azusa after realizing her protective nature, as well as having no desire to turn her into medicine and joins her family as her third adoptive daughter. Azusa names her, and Sandra forms close bonds with Falfa and Shalsha. Though initially wary of Halkara due to her prejudice against elves, Sandra gradually warms to her. She possesses extensive knowledge of agriculture and crop cultivation. ; : :A pine spirit woman who resides in a temple. She is a being who mediates marriages. After Azusa helps resolve her problem, she creates another temple in Azusa's village. She forms good terms with Mega-mega. ; : :An about 60,000 to 70,000-year-old jellyfish spirit and wandering artist woman. She can make jellyfish glow. Her artwork is also quite disturbing. ; : :The goddess. The very being who reincarnated Azusa into this world. When she comes to Azusa's world, she assumes the alias Mega-mega. It is later revealed she was demoted due to the fact that her method of reincarnating people as immortal young women is becoming an issue for all the other gods. She is rivals with Nintan and has a good relationship with Misjantie. ; : :A ghost girl. Sovereign of the ghost's kingdom of the dead. She died at 15 years old, and about 5,000 years have passed since her death. Since then, she had refused to come out from her tomb because she thinks her people are boring and does not have any friends due to her status as queen. After befriending Rosalie, she forms an alliance with Pecora. ; : :A ghost girl who serves as Muu's maid and chief minister. ; : :The goddess of time, who is long worshipped in Azusa's world. She is Mega-mega's rival. Nintan is very stubborn and arrogant, known to turn people into frogs if they oppose her. Azusa and Mega-mega go to confront her after she disapproves of Mega-mega's virtue stamp card antics. After Azusa beats her in a match, Nintan establishes a good relationship with her and agrees to let go of her personal issues towards Mega-mega's methods. ; :A slime spirit girl born after Falfa and Shalsha. ==Media==
Media
Light novels Originally, the series was published by Kisetsu Morita on the user-generated web novel site Shōsetsuka ni Narō in 2016. The publisher SB Creative acquired the series and then began publishing it on their GA Novel imprint as a light novel in January 2017. Twenty-nine volumes have been released as of January 2026. The series is set to end with the release of its 30th volume on August 8, 2026. In the volumes 5 to 7, 20, and 21 of the light novel, a special story about the character Beelzebub was published at the end of those volumes. In September 2019, those stories were compiled into its own volume and the spin-off, called , published by SB Creative on the GA Novel imprint with Kisetsu Morita and Benio as the author and illustrator, respectively. In the volumes 8 to 10 of the light novel, another spin-off light novel called , a special story about the character Halkara was published at the end of those volumes. In the volumes 11 to 13, 16, and 18 to 19 of the light novel, another spin-off light novel called a special story about the character Laika was published at the end of those volumes. In the volume 17 of the light novel, another spin-off light novel called , a special story about the character Wynona was published at the end of that volume. Manga In June 2017, Square Enix began publishing a manga adaptation of the series by Yūsuke Shiba in their online website and smartphone app Gangan Online, with seventeen volumes released as of December 2025. A manga adaptation of the spin-off light novel I Was a Bottom-Tier Bureaucrat for 1,500 Years, and the Demon King Made Me a Minister was launched on Square Enix's Gangan Online website and smartphone app, with Meishi Murakami reprising his work. A manga adaptation of the spin-off light novel Red Dragon Women Academy was launched on Square Enix's Manga UP! smartphone app, with Hitsujibako reprising his work. Anime An anime television series adaptation was announced during a livestream for the "GA Fes 2019" event on October 19, 2019. It is animated by Revoroot and directed by Nobukage Kimura, with Tatsuya Takahashi handling series' composition, Keisuke Goto designing the characters, and Keiji Inai composing the series' music. The series aired from April 10 to June 26, 2021, on AT-X and other networks. The opening theme song is , performed by Aoi Yūki, while the ending theme song is "Viewtiful Days!", performed by Azumi Waki. Crunchyroll streamed the series outside of Asia. In the South-eastern parts of Asia, Muse Communication licensed the series. The series was broadcast on Animax Asia in the region. In January 2022, it was announced that the series would receive a second season. It is animated by Teddy and directed by Kunihisa Sugishima, with Naohiro Fukushima handling series' composition, Hikaru Kodama designing the characters, and Keiji Inai returning to compose the series' music. The season aired on April 5 to June 21, 2025. The opening theme song is "So Lucky", performed by Yui Ogura, while the ending theme song is , performed by Aguri Ōnishi. Season 1 (2021) Season 2 (2025) ==Reception==
Reception
The light novel ranked ninth in 2019 in Takarajimasha's annual light novel guide book Kono Light Novel ga Sugoi! in the category. ==Notes==
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