Question: Which seinen manga featuring Kei Kurono, and Masaru Kato, did Hiroya Oku write?

Context paragraphs:
Inuyashiki: Inuyashiki (いぬやしき ) is a Japanese science fiction manga series written and illustrated by Hiroya Oku.  "Inuyashiki" debuted in the January 2014 issue of Kodansha's "seinen" manga magazine, "Evening".  s of May 2017 , nine compilation volumes have been published.

List of Gantz episodes: The anime series "Gantz" is an adaptation from the manga with the same name written and illustrated by Hiroya Oku.  The series, produced by Gonzo and directed by Ichiro Itano, aired in Japan on Fuji Television and AT-X.  "Gantz" tells the story of a teenager named Kei Kurono who dies in a train accident and becomes part of a semi-posthumous "game" in which he and several other recently deceased people are forced to hunt down and kill aliens hidden in Japan.

Masaru Kato: Masaru Kato (加藤 大 , Katō Masaru , born May 7, 1991) is a Japanese footballer who plays as a midfielder.

Hiroya Oku: Hiroya Oku (奥 浩哉 , Oku Hiroya , born September 16, 1967) is a manga artist who is the creator of "Gantz", "Zero One" and "HEN", all of which have been serialized in "Weekly Young Jump".  He is finished working on his most renowned manga, "Gantz", which began in July 2000.  His manga often contain explicit violence and gore, as well as sexual situations.

List of Gantz chapters: The chapters of the Japanese manga "Gantz" are written and illustrated by Hiroya Oku, and have been published in the Japanese manga anthology "Weekly Young Jump" since its issue 32 published in 2000.  The plot follows a teenager named Kei Kurono and his friend Masaru Kato who die in a train accident and become part of a semi-posthumous game in which they, and several other recently deceased people, are forced to hunt down and kill aliens.

Gantz: Gantz (Japanese: ガンツ , Hepburn: Gantsu ) is a Japanese manga series written and illustrated by Hiroya Oku.  "Gantz" tells the story of Kei Kurono and Masaru Kato, both whom died in a train accident and become part of a semi-posthumous "game" in which they and several other recently deceased people are forced to hunt down and kill aliens armed with a handful of futuristic items, equipment, and weaponry.  Both the manga and anime are noted for their heavy violence and sexual content.

Seinen manga: "Seinen" manga (青年漫画 ) are manga marketed toward adolescent boys and men old enough to read kanji.  In Japanese, the word "seinen" literally means "youth," but the term "seinen manga" is also used to describe the target audience of comics like "Weekly Manga Times" and "Weekly Manga Goraku" which are aimed at men from their 20s to their 50s.  Seinen manga are distinguished from shōnen manga which are for younger boys, as well as the seijin-muke manga (成人向け漫画 ) which focus on sex, although some seinen manga like "xxxHolic" share some similarities with "shōnen" manga.  Seinen manga can focus on action, politics, science fiction, fantasy, relationships, sports, or comedy and while they may contain sexual content (as well as other mature material), it remains predominantly more infrequent than in the seijin-muke manga.  The female equivalent to seinen manga is josei manga.

Shion no Ō: Shion no Ō (しおんの王 , lit.  "Shion's King") , subtitled "The Flowers of Hard Blood", is a Japanese mystery manga written by Masaru Katori and illustrated by Jiro Ando.  It is published by Kodansha in the seinen manga magazine "Afternoon", and is collected in eight bound volumes.  It has been adapted as a twenty-two episode anime television series by Studio Deen, which aired in Japan between October 2007 and March 2008.  A video game for the Nintendo DS was released on April 10, 2008 by Mainichi Communications.

Hen (manga): Hen (変 ) is a seinen manga which was the first work created by manga artist Hiroya Oku, who is best known for "Gantz".

Gantz (film): Gantz is a series of two Japanese live-action films released in 2011, based on the manga series of the same name by Hiroya Oku.  The first was simply titled Gantz, and the second was titled Gantz: Perfect Answer.  The first film, starring Kazunari Ninomiya and Kenichi Matsuyama, follows two highschool students who are transported to an alternate world upon their deaths.  In this alternate reality, a black globe gives them missions to kill aliens, a mission that the characters continue in the second installment of the series.  A film "Another Gantz" also aired on television between the two films, and follows an investigator.

Supporting paragraphs: Hen (manga) Gantz
Answer: Hen