ONE is the pseudonym of a Japanese manga artist and webcomic creator, born on October 29, 1986, in Niigata Prefecture and raised in Saitama Prefecture. He adopted this pen name to maintain his privacy, and his real name has not been publicly disclosed. His interest in manga began in childhood, significantly influenced by reading Yoshito Usui's comedy series Crayon Shin-chan, which his parents bought for him to pass the time. This early exposure inspired him to start drawing his own comics, a practice he continued through middle and high school.

ONE began his career by self-publishing original webcomics on his personal website. In July 2009, he started posting a short version of One-Punch Man online as an exercise to learn a manga-drawing software program. Despite its intentionally rough and rudimentary art style, the series gained massive popularity on the Japanese internet for its humorous premise and compelling storytelling. Recognizing the potential of his work, ONE later partnered with professional illustrator Yusuke Murata. In June 2012, they began serializing a professionally remastered version of One-Punch Man in Shueisha's online magazine Tonari no Young Jump, with ONE providing the story and original concepts while Murata handled the detailed artwork.

Also in April 2012, ONE officially debuted as a professional manga artist when he began serializing another original work, Mob Psycho 100, in Shogakukan's web comic magazine Ura Sunday. The series concluded in December 2017. Following this success, he wrote a spin-off manga titled Reigen, which focuses on a supporting character from Mob Psycho 100 and was released as a single volume in 2019. He has also created other serialized works, including Makai no Ossan, which ran from 2012 to 2014. In November 2022, ONE began a new series called Versus in Kodansha's Monthly Shonen Sirius magazine, for which he provides the story and original concept, with art by Kyotaro Azuma and story composition by bose. This project represents his first work created as a purely original writer, without drawing the manga himself, and originated from an idea he had been developing for several years about multiple fantasy worlds colliding.

The popularity of ONE's manga led to major anime adaptations. One-Punch Man received its first anime season in 2015, followed by a second season in 2019. Mob Psycho 100 was adapted into an anime with its first season airing in 2016, the second in 2019, and a third season concluding the story in 2022. A spin-off anime focused on the character Reigen also aired in 2018. ONE is credited as the original creator for these productions, with his name appearing in the opening credits and official materials for series such as Mob Psycho 100 II, Mob Psycho 100 REIGEN: The Miraculous Unknown Psychic, and the first season of One Punch Man.

A central and defining aspect of ONE's artistic identity is his distinctive, unpolished drawing style, which prioritizes storytelling, humor, and character expression over technical refinement. Critics and fans often note that his raw linework and simplified character designs have a unique charm and effectively convey motion and emotion. His work is known for deconstructing typical shonen manga tropes, particularly those involving constant power escalation. Both One-Punch Man and Mob Psycho 100 feature protagonists who are already the most powerful beings in their respective worlds, shifting the narrative focus away from training and tournaments toward themes of personal struggle, finding meaning in life, dealing with boredom, and navigating social relationships. The protagonist Saitama's overwhelming strength leads to existential ennui, while Mob's immense psychic powers are secondary to his desire for self-improvement and emotional control. ONE has stated in interviews that he enjoys creating protagonists who have already become the strongest, which allows him to concentrate on different perspectives of background and storytelling.

ONE's significance in the manga industry stems from his pioneering success as a webcomic creator who transitioned to professional print publication without sacrificing his unique vision. His career demonstrated the power of online platforms as a launchpad for new talent and proved that a compelling narrative and strong comedic voice could overcome a lack of conventional artistic polish. In 2017, he received the prestigious 62nd Shogakukan Manga Award in the shonen category for Mob Psycho 100. Beyond his creative work, ONE has also been publicly vocal on industry issues. In early March 2026, he publicly stated on social media that he would not work with the Manga One platform unless it clearly condemned sexual harm against minors, following a scandal in which the company was found to have hired individuals with convictions for sexual offenses against minors. This stance highlighted his commitment to ethical standards within the manga publishing industry.