Kill Blue

Kill Blue (キルアオ) is a Japanese manga series written and illustrated by Tadatoshi Fujimaki. It began serialization in Shueisha's Weekly Shōnen Jump magazine in April 2023; as of June 2024, five volumes have been released.

Plot
Juzo Ogami is a 40-year-old who works for the Z.O.O. assassin syndicate as their prized hitman. During a job taking out criminals working with the genetic manipulation company Mitsuoka Pharmaceuticals, Ogami is stung by a wasp that modifies his DNA, regressing his age to that of when he was 12. Unable to resume work as a hitman due to his stature, the head of Z.O.O. gives Ogami another assignment while they work on an antidote: attend a middle school the head's daughter is applying to and judge if it is safe. Ogami, due to having no formal education, turns out to love middle school, and must balance his time as a student and an assassin. He must also deal with Noren Mitsuoka, the heiress of Mitsuoka Pharmaceuticals, who may be the key to figuring out how to age Ogami back to normal.

Publication
Written and illustrated by Tadatoshi Fujimaki, the series began serialization in Shueisha's Weekly Shōnen Jump magazine on April 17, 2023. As of June 2024, the series' individual chapters have been collected into five tankōbon volumes.

Viz Media and Manga Plus are publishing the series in English simultaneously with its Japanese release. Viz Media began releasing the volumes digitally in July 2024.

Chapters not yet in tankōbon format
These chapters have yet to be published in a tankōbon volume.
 * 44. "A Ride on the Hit Man Express"
 * 45. "Yoshitsune and Johnny"
 * 46. "Keep Your Hands Off the Home Ec Club"
 * 47. "Keep Your Hands Off the Home Ec Club, Part 2"
 * 48. "Vs. JARDIN, Round 2"
 * 49. "The Legend vs. The Beast"
 * 50. "The Legend vs. The Beast, Part 2"
 * 51. "Conclusions"
 * 52. "Out of the Frying Pan"
 * 53. "Vacation Home"
 * 54. "The Mitsuoka Vacation Home Hexagon Manor Murder Case"
 * 55. "The Night Pool & the Sealed Door"
 * 56. "The Mitsuoka Dungeon"
 * 57. "The Mitsuoka Dungeon, Part 2"
 * 58. "The Mitsuoka Dungeon, Part 3"
 * 59. "The Mitsuoka Dungeon, Part 4"
 * 60. "The Mitsuoka Dungeon, Part 5"
 * 61. "On the Outs"

Reception
The series was ranked seventh in the Nationwide Bookstore Employees' Recommended Comics of 2024 list. The manga has been nominated for the 2024 Next Manga Award in the print category.

Kaylie Fielden of Screen Rant felt the plot was unique among other hitman manga and praised the beginning chapters. Robbie Pleasant of Multiversity Comics praised the artwork and characters. Regarding the story, Pleasant felt that it has some worrying elements but nonetheless handled them well. Kara Dennison of Otaku USA described the series as "Case Closed with added violence".