is a Japanese web manga series written and illustrated by . It was published on Shueisha's web platform Shà Ânen Jump+ from December 2021 to March 2022, with its chapters collected in two volumes. An original net animation (ONA) adaptation produced by and TBS Television was released from June to August 2025.
In 2016, Nueinukf, an alien hailing from the Happy Planet, crash-lands on Earth on his mission to spread happiness to others. After evading capture, he comes across Shizuka Kuze, a 9-year-old girl who is bullied at school and only finds solace with her Border Collie, Chappy. Shizuka, noting that he resembles an octopus, names the alien Takopi. Takopi decides to use his planet's Happy Gadgets to help Shizuka, but after seeing her, face scratched and bruised all over while holding Chappy's leash, Shizuka asks for one of Takopi's gadgets and uses it to commit suicide. Realizing the gravity of the situation, Takopi uses a Happy Camera to travel back in time, hoping to prevent Shizuka's suicide.
In one of these loops, during a confrontation between Shizuka and her bully Marina Kirarazaka, whose father had an affair with Shizuka's mother, Takopi accidentally hurls the Camera at Marina, breaking it after failing to save Chappy in 101 attempts, killing her and preventing them from reversing time again. Desperate to conceal the crime, Takopi, with help of Shizuka's classmate, Naoki Azuma, buries Marina's body inside one of his gadgets before assuming her identity. The ruse quickly unravels: Takopi's imitation of Marina is unconvincing, and a group of workers soon stumbles upon the hidden corpse. Meanwhile, Shizuka exploits Naoki's deteriorating mental stateâÂÂhis spiral into paranoia over hiding the crime, his frantic attempts to save her dog, and the crushing weight of being compared to older brother Junya and condemnation after a poor grade. Ultimately, Takopi tries to reason with Shizuka, preventing her from making anymore mistakes, but Shizuka knocks him out with a rock.
An unconscious Takopi recalls his previously erased memories; he initially came to Earth in 2022 to spread joy. The first person he ran into however was not Shizuka but Marina who lived in an abusive household. With Takopi's help, Marina's life begins to improve and she starts dating Naoki. But when Naoki leaves Marina for Shizuka, Marina regrets not killing Shizuka in fourth grade. Later, Marina's mother finds out about the relationship, but she kills her in self-defense. This failed timeline leads Takopi to plot killing a 9-year-old Shizuka in the past, which caused the erasure of his memories as a violation of Planet Happy's law, making him forget his original plan upon traveling back in time.
Returning to where Marina and Shizuka met, Takopi is consoled by Naoki, who thanks him for their friendship and returns to him his Camera. Months later, Takopi finds Shizuka looking for Chappy, and apologizes for initially causing her pain. He ultimately sacrifices himself to reactivate the Camera, rewinding to 2016 back when Shizuka met Takopi. Afterward, Shizuka is able to tearfully apologize to Marina, reminiscing of Takopi upon noticing her sketch of him, while Naoki reconciles with Junya and his friends as Takopi wishes them happiness before disappearing. Six years later in 2022, Shizuka and Marina remain best friends growing up together.
Written and illustrated by , Takopi's Original Sin was published on Shueisha's web platform Shà Ânen Jump+ from December 10, 2021, to March 25, 2022. Shueisha collected its 16 chapters in two volumes, released on March 4 and April 4, 2022.
Shueisha's Manga Plus service published chapters of the series in English simultaneously with their Japanese release. In February 2023, Viz Media announced that it licensed the manga for English publication; the series was released as a single volume on November 21 of that same year.
In December 2024, it was announced that the series would receive an anime adaptation. It was later revealed to be an original net animation (ONA) produced by , with TBS Television handling planning and production duties. The six-episode miniseries was directed and written by Shinya Iino, with character designs and chief animation direction handled by Keita Nagahara, and music composed by . The series was released from June 28 to August 2, 2025, on various streaming platforms, including Netflix, Amazon Prime Video, Abema, and U-Next. The opening theme song is , performed by Ano, while the ending theme song is , performed by . Crunchyroll streamed the series outside Asia, with a dub being later produced. Medialink licensed the series in the Asia-Pacific for streaming on Ani-One Asia's YouTube channel.
Takopi's Original Sin won the Excellence Prize at the 51st Japan Cartoonists Association Awards in 2022. The series ranked third in the 2023 edition of Takarajimasha's Kono Manga ga Sugoi! list of best manga for male readers. The series ranked ninth on "The Best Manga 2023 Kono Manga wo Yome!" ranking by Freestyle magazine. It was nominated for the 16th Manga Taishà  in 2023, and ranked 10th out of 11 nominees; it has been nominated for the 27th Tezuka Osamu Cultural Prize in the same year. The manga was nominated for the 54th Seiun Award in the Best Comic category in 2023.
In February 2022, it was reported that the series surpassed the 2 million views per day on the Shà Ânen Jump+ platform. The first volume sold 41,277 copies in its first week, and the second volume sold 198,505 copies in its first week. By May 2022, the manga had over 1.2 million copies in circulation, including digital versions.