The Secret Man

Originally published as a doujin in the Ishimori Fan Club magazine before its official release.

All Digital Editions of the Manga Have Been Delisted as of 2019

(from ebookjapan):
Fuji, someone has stolen a hydrogen bomb from a U.S. B-52 super heavy bomber that crash-landed on Mt. Fuji and hidden it somewhere! Junior high school student Kenji Shiromaru's older brother Ichiro, a secret agent of the United Nations, is killed while pursuing this case. Kenji, following in his brother's footsteps, sets out to the headquarters of Gozo Inuyama, an arms dealer who is behind the incident, but the hydrogen bomb is taken away by a U.S. Air Force colonel and ......!? In addition to the title story, two action short stories are also included.