Akio Ōtsuka Is Voicing a Slime
The casting carries over from the promo videos and voice drama Drecom produced for the novels, so fans who followed the books already know these voices. Manaka Iwami (Tohru Honda in Fruits Basket, Akane Kurokawa in Oshi no Ko) plays Leen, the confident, slightly devilish heroine. Chiaki Kobayashi (Gabimaru in Hell's Paradise, Mash Burnedead in Mashle) plays Hakura, the adventurer she pulls into her orbit. And Akio Ōtsuka, the voice of Batou in Ghost in the Shell and Solid Snake in the Metal Gear games, plays Ao. Who is a slime.
Ōtsuka seems fully aware of how fun that sounds. In his comment accompanying the announcement on PR TIMES, he says he first encountered the work at the audition, pegs it as a road-movie kind of story (a genre he calls a personal favorite), and describes his part as "a veteran monster at a young protagonist's side." His verdict: doesn't that already sound interesting?
Iwami notes she has been with Leen since the original novel promo video. She describes Leen as a character who reads as breezy and full of herself at first but is knowledgeable and genuinely dependable, and says her comic back-and-forth with Hakura balances the story's heavier themes.
A Witch's Heir, a Witch Hunter, and One Troublesome Road Trip
The novels follow Leen, a descendant of Ringreen, the primordial witch said to have once saved the world. Leen inherited the ability to command any monster. Deep in a quiet forest she finds Hakura, an adventurer nicknamed "Witch Hunter," dying after a fight with a vicious monster. She saves his life with a pointed question (live, or be put out of your misery?), hires him as her bodyguard, and the two set off on a journey with her attendant slime Ao. Her special power keeps attracting exactly the kind of monster trouble nobody wants to deal with.
A unanimous jury handed the series the grand prize at the 2nd Drecom Media Award, the novel contest run by Tokyo-based publisher Drecom. This adaptation makes it the first Drecom Media Award winner ever turned into an anime, a milestone the company is clearly proud of: the release frames the whole announcement around it.
The Team at project No.9
Chihiro Kumano directs the series at project No.9, with Satoru Sugisawa (杉澤悟) handling series composition and Akane Kasasagi (鵲あかね) on character design. Shirabii, the illustrator of the original novels, is credited for the original character designs. Kumano's comment is the most striking of the batch: he describes the source material as having the odd, nostalgic pull of a dream you want to fall back asleep into, and says he wants to depict "both the beauty and the cruelty of this world as a hymn to all creation."
Author Damu Amato, in his own comment, admits he still can't quite believe the childhood dream came true and notes the broadcast is still a little way off. That is the closest thing to schedule information in the announcement; no premiere window has been given.
Alongside the anime news, Drecom launched an official site at mamomusu.com and revealed a teaser visual for the series.
Looking Ahead
There is more on the calendar than the anime itself. A manga adaptation drawn by Yū Satō starts serialization in September 2026 on Drecomi+, Drecom's web manga site, and a free preview of chapter 1 is already up there in Japanese. On the novel side, volume 3 arrives in Japan on July 10, 2026, with volumes 1 and 2 on sale now under the DRE Novels label.
International fans can read the source material legally right now: J-Novel Club publishes the novels in English as Heir to a Monstermancer. No streaming partner or international broadcast plans for the anime have been announced yet, and given the author's hint that the premiere is still some way off, that news will likely come with the release-window reveal.