In this anime series, scientists goal "tallying humans" will make universal friendship, but they'a propos kidnapped by an evil organization bearing in mind utterly swap plans.

Taking place in the year 1937 on the eve of World War II, the story involves a mysterious spy training organization known as the "D Agency." The organization is established by Lieutenant Colonel Yuuki from the Imperial Japanese Army. His ideals lead him to recruit people beyond military academy graduates and personnel, while training them to become skilled agents in arts of manipulation. These agents would become a specialized team to conduct operations. One such antihero agent, under the name Jirou Gamou, goes on a harrowing mission to uncover secret documents titled "Black Notes," while battling forces from within and without his own ranks.

Taking place in the year 1937 on the eve of World War II, the story involves a mysterious spy training organization known as the "D Agency." The organization is established by Lieutenant Colonel Yuuki from the Imperial Japanese Army. His ideals lead him to recruit people beyond military academy graduates and personnel, while training them to become skilled agents in arts of manipulation. These agents would become a specialized team to conduct operations. One such antihero agent, under the name Jirou Gamou, goes on a harrowing mission to uncover secret documents titled "Black Notes," while battling forces from within and without his own ranks.

Not so long ago, mysterious structures called dungeons began appearing all over the world. No one knows what they are or how they came to be, but adventurers and armies around the world instantly took interest in them. Thousands set out to explore the dungeons, but so far, not a single person has returned. In a Parthevia port, a young boy is about to make a name for himself. Sinbad is good-natured, strong, and craving adventure. A kind deed leads to his meeting with Yunan, an enigmatic traveler who is far more powerful than his frivolous personality lets on. Yunan instructs Sinbad to attain the "power of the king" and change the world—by conquering a dungeon. The eager boy readily accepts, setting out on the grand adventure he so craved. Taking place 15 years before the events of the original series, Sinbad no Bouken chronicles Sinbad's youth as a dungeon conqueror. Along the way, the budding adventurer and merchant will have to face many obstacles, but anything is possible with the power of a king. This OVA was released prior to the TV series.