In the story, Kurono is a teenager who feels forced to save a man from a subway train alongside his childhood friend Masaru Kato, but is killed in the process.

To make him the Gantz character readers would identify with, the author gave him traits such as his sense of insecurity, fears and other complexes.

[2] Before the manga started serialization, Oku told his assistants that with Kurono's exception, all the major characters from the series would die in order to surprise readers with plot twists.

[5] Gantz: O director Yasushi Kawamura said that as a result of Kato replacing Kurono as the protagonist of the film, he felt unsure of the audience's reaction even if they had not read the original manga.

[6] For the live-action series, director Shinsuke Sato said that Ninomiya was perfectly cast for the role, that he visually resembled the manga character and represented the current audience.

[9] Introduced in Gantz's first chapter Kei is a 10th grader who, with his childhood friend, Masaru Kato, is struck by a subway train while trying to help a derelict who had passed out on the tracks.

They are subsequently summoned by a being known as Gantz that has power over their lives and periodically enlists them on missions to kill aliens hiding amongst humanity.

In the beginning, he is a fairly selfish character, with a penchant for sexual perversity with Kei Kishimoto, and often ends up being the reluctant hero.

[11] After building the team into a capable and successful unit and reviving some of his former friends, Kurono retires from the game at the request of his comrades.

As the original Kurono searches for Tae, the copy assembles with other Gantz members from across the world who wish to save humanity from the aliens.

[18] In the live-action films, Kurono goes through many events from the original manga but is unable to remember Tae following his removal from Gantz's games.

James Musgrove of IGN found his anime rendition to have "all-too-human motivations" juxtaposed with an emergence of his "hidden good side" as the story progresses, and implied that he was an unconventional protagonist.

[19] In the live-action review, Otaku USA called the character an "uneven protagonist" similar to how Kurono is portrayed in the manga and praised his connections with Kato and Kishimoto.

[23] Mania Entertainment stated that Kurono has "halfway decent hero material wrapped up in a slimeball package" for how he manages to fight his enemies based on his own childhood when he was used to face multiple challenges.

AnimeFringe described Kurono as "the token angst-filled high school student" and criticized his focus on puberty, finding Masaru Kato much more likable due to their differences.

[26] THEM Anime Reviews similarly found Kurono to be an unlikable character, described him as a "soulless monster" and went on to say "he's mean, extremely selfish, very cynical, and you almost get the feeling he's happy that way, or at least unapologetic.

[28] Anime News Network felt that while Kurono underwent multiple personality changes across the manga, the site stated Oku lacked the talent to make it appealing and heavily criticized his overshadowing relationships with secondary characters.

[30] UK Anime Network praised Kazunari Ninomiya's acting in the second live-action film which manages to make the character more appealing.

[31] While finding Kurono more likable than his manga persona based on his growth across the first film and his romantic relationship, Anime News Network stated that fans might miss his original character traits.