Akito Tenkawa is a central figure in the events of the film, portrayed five years after the conclusion of the television series. Originally a native of Mars, he survived the destruction of his home colony during the initial Jovian conflict, an event that left him with a deep-seated trauma regarding combat. Before the movie's events, Akito had moved past his reluctance to fight, became a celebrated pilot, and started a life with his childhood friend and commanding officer, Yurika Misumaru. He had finally achieved his dream of working as a chef, opening a ramen restaurant and proposing to Yurika. Their marriage, however, was short-lived, as the shuttle taking them on their honeymoon was destroyed in a presumed fatal accident.

In The Prince of Darkness, it is revealed that Akito survived, but the cheerful and somewhat reluctant young man from the series is gone. He and Yurika were kidnapped by a faction known as the Martian Successors, who sought to exploit their abilities as Class-A Boson Jumpers. While Yurika was placed into a state of hibernation and integrated into a Boson Jump calculation unit, Akito was subjected to brutal experiments. These procedures fundamentally altered his biology, stripping him of much of his humanity and destroying several of his senses, most notably his sense of taste. This loss is particularly tragic, as it robbed him of his lifelong ambition to be a chef.

Driven by the dual desires of rescuing his wife and exacting vengeance on her captors, Akito has transformed into a grim, solitary figure. He operates from the shadows, piloting a powerful, dark-colored custom Aestivalis called the Black Sarena, which is part of Nergal's One-Man, One-Ship Project. His missions are carried out from a corvette named the Eucharis, alongside his partner Lapis Lazuli, another victim of experimentation whose emotional capacity was destroyed. Their partnership is a symbiotic one, with each compensating for what the other has lost. To his former friends and crewmates, Akito has become a ghost, known only as the Black Ghost, a rumored figure who conducts lightning-fast raids on Martian Successor bases across the solar system using his ability to Boson Jump at will.

When he is eventually reunited with the crew of the Nadesico B, the contrast is stark. He is cold, distant, and rejects their attempts to reconnect, insisting that the person they once knew is dead. In a poignant moment, he gives his secret ramen recipe to Ruri Hoshino, the young captain, explaining that he can never cook it for her again. His personality is now defined by a quiet, simmering intensity and a ruthless focus on his mission. His primary motivation is no longer a simple desire to cook or live peacefully, but a relentless pursuit of the Martian Successors, culminating in a personal and deadly confrontation with his primary tormentor, Hokushin. Despite finally succeeding in saving Yurika, Akito chooses to disappear at the film's conclusion, his future uncertain. His notable abilities include being a Class-A Boson Jumper, allowing instantaneous travel across vast distances, and he is a highly skilled mecha pilot, now augmented by his grim determination and the advanced technology of the Black Sarena. A physical manifestation of his trauma is that his body will luminesce when he experiences intense emotional states.