A man who exterminated pests in his previous life continues his work in another world.
Utilizing his knowledge from his previous life, Naoki Komuro makes a living exterminating monsters. However, even though he only targets weak monsters, their numbers are anything but ordinary.
As he started to earn a stable income and settled into an apartment on the second floor of a pharmacy, he became aware of a strange change occurring within himself.
The protagonist, Naoki, a former cleaner and pest exterminator from Earth, finds himself reincarnated in a fantasy world after a fatal accident. Three weeks into his new life, he has managed to establish a basic living by taking on cleaning and pest control jobs, utilizing his past experience. He joined the Adventurer's Guild for training but discovered he lacked any talent for swordplay or magic. His current town is a medieval-esque settlement where magic is used for lighting and various demi-humans like beastmen and elves coexist with humans.
Naoki secures a cleaning job at an elf apothecary owned by the ancient and sharp-eyed Camilla. After completing the job and receiving his payment of 50 knots, he heads to the Adventurer's Guild to report his completion. At the guild, he's approached by a fox-eared beastwoman receptionist, who offers him a lucrative job: exterminating rat-like monsters, "Masmascal," in the town's sewers. This is a welcome opportunity as it promises good pay, allowing him to save up for his own room.
The next day, Naoki visits the town hall to receive the sewer map and details of the extermination quest. He learns that each Masmascal tail brought in will earn him 5 knots. He then returns to Camilla's apothecary to inquire about rat poison. Camilla, after some negotiation, sells him a potent monster-damaging potion at a discounted price, seemingly taking a liking to him. She also informs him that the apartment above her shop is available for rent. Naoki, now with a potential place to live and a promising job, gathers ingredients from a butcher to create his own rat poison, mixing them with the potion. He crafts about 100 "rat poison dumplings" and prepares to tackle the sewer infestation.
Naoki enters the sewers, equipped with a helmet light. He strategically places his homemade poison dumplings, encountering Masmascal and collecting their tails as proof of extermination. He efficiently dispatches them, using his environment to his advantage. After collecting 10 tails, he reports back to the town hall and receives 50 knots. He learns about the world's level system and skills, discovering that his actions have unexpectedly raised his level significantly. He also acquires the "Language Ability" skill, allowing him to communicate fluently.
He continues his extermination efforts, leveling up rapidly. He also learns about "Cleanup" and "Alchemy" skills and begins to invest his skill points, quickly mastering them. He rents the apartment above Camilla's shop and begins to settle in.
Naoki's rapid leveling and unusual methods attract attention. He's tasked with a more dangerous mission: exterminating a swarm of "Vespa Hornet" monsters in a derelict mansion. He devises a unique strategy involving magical traps and explosive preparations, ultimately defeating the formidable creatures. This feat further boosts his level and reputation.
Following the Vespa Hornet incident, Naoki's slaves, Balzac and Seila, are tasked by the Adventurer's Guild to assist in identifying the victims in the mansion. This leads to further complications and responsibilities for Naoki, who finds himself increasingly entangled in the lives of others. He also begins to explore the world's history and geography with the help of the guild receptionist, Irene, and learns about the existence of magic circles and advanced crafting skills.
Naoki's journey continues as he navigates the complexities of his new life, balancing his desire for a quiet existence with the growing responsibilities thrust upon him. He continues to develop his unique skills and adapt to the challenges of this new world, all while trying to maintain his simple lifestyle.
 | Wikipedia https://en.wikipedia.org › wiki › Kaku... "Exterminator" (Kujonin) is a Japanese light novel series written by Hana Kuroko and serialized on the website "Let's Become a Novelist" since September 2015. The published version was published by MF Books (KADOKAWA) from June 2016 to 2019. |
| Wikipedia https://en.wikipedia.org › wiki › Exterminator |
 | https://x.com/hanabokur0 |
 | Become a Novelist https://ncode.syosetu.com › ... Exterminator. Author: Hana Kuroko. A story about a man who used to be a pest exterminator, but now also exterminates pests in another world. Naoki Komuro uses his knowledge from his previous life to exterminate monsters, but he only exterminates weak monsters... |
 | Amazon.jp https://www.amazon.co.jp › Extermination... Book Summary: Naoki Komuro uses his knowledge from his previous life to exterminate pests and vermin, but even though he only exterminates weak monsters in the other world, there are still many of them. He begins to earn a steady income and takes over the pharmacy business... |
| Become a Novelist https://mypage.syosetu.com › ... September 22, 2025: Exterminator (Undiluted) Volume 9 is now on sale! August 30, 2025: Abandoned Dungeon Trekking Volume 2 is now on sale! Activity Report List... |
 | Kinokuniya Bookstore Webstore https://www.kinokuniya.co.jp › ds... The Exterminator soon embarks on a journey to explore this world! The definitive alternate world story begins! About the author. Hanabokuro is originally from Hokkaido. In May 2015, he began publishing "Exterminator - Jumpsuit..." |
| Amazon.jp https://www.amazon.co.jp › Extermination... Hana Kuroko is originally from Hokkaido and currently lives in Tokyo. She began serializing her work on a novel submission website in May 2015. She has created a unique story by portraying a realistic protagonist and incorporating social satire and environmental issues into her work. |
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 | Bookmeter https://bookmeter.com › authors Hana Kuroko's Recommended Books Ranking List: Exterminator (1) (Kadokawa Comics Ace) · 321; Exterminator (2) (Kadokawa Comics Ace) · 275; Exterminator (3) (Kadokawa Comics Ace) · 228. |
 | amazon.co.jp https://www.amazon.co.jp › Exterminator-1-Kadokawa Comics Edition... |
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