OVA
Description
Gajou Akatsuki is the father of Kojou and Nagisa Akatsuki and the ex-husband of Mimori Akatsuki. Known as the Returnee from the Netherworld, he lost half of his body during an incident known as the Fairy's Coffin incident. Following these events, he asked Natsuki Minamiya to look after his children while he embarked on a journey to find a, as he put it, cure for them.

In terms of personality, Gajou is portrayed as a jolly and fun-loving middle-aged man who socializes with ease. He has a love for challenges and a tendency to engage in risky behavior, such as fighting a giant magic-fueled golem with guns. This carefree and sometimes abrasive nature is particularly evident in his relationship with his son, Kojou, whom he jokingly but harshly teased about his romantic prospects. His approach to parenting includes taking his children on dangerous expeditions, a habit that clearly displeased his ex-wife. His personality is noted to be the source of many of Kojou's character traits, including his awkward timing in certain situations. Despite his irresponsible and careless behavior as a parental figure, the underlying love between him and his son remains.

Gajou plays a significant role in the story of Strike the Blood II. He appears during the arc focusing on the fugitive Fourth Primogenitor, where he and Nagisa become central figures in the events. He arrives on Itogami Island, briefly encounters his son and Yukina Himeragi, and soon after leaves the island with Nagisa. This leads to a situation where he is captured and imprisoned at a temple near Lake Kannawa by Lion King Organization miko Yuiri Haba and Shio Hikawa. During the Knight of the Sinful God arc, he escapes imprisonment when the area comes under attack by demon beasts, and he works alongside Shio Hikawa to fight off the creatures and make his way to the frozen lake to confront Nagisa, who has been possessed by Avrora.

Key relationships define his character. His relationship with his son Kojou is rocky and complicated, built on a mixture of teasing, carelessness, and genuine affection. He has a protective relationship with his daughter Nagisa, as much of his plotline in this season revolves around her wellbeing. He shares a professional and cooperative relationship with Shio Hikawa, as they fight together and he entrusts Nagisa to her care. His former relationship with his ex-wife, Mimori, is marked by disagreement over his parenting style and dangerous lifestyle.

Regarding development, Gajou's narrative purpose in Strike the Blood II is to reveal more about the Akatsuki family's past and present. He serves as a catalyst for the climax of the second season's story arc, directly setting into motion the events of the Knight of the Sinful God arc by leaving the island with Nagisa. His actions force his son, Kojou, and other characters to respond to the crisis he is involved in.

Gajou possesses several notable abilities stemming from his status as the Returnee from the Netherworld. He gained the ability to pass through solid objects, effectively becoming intangible like a ghost. He also has a heightened sense for detecting magical power from mystical objects or creatures. As an archaeologist specialized in mystical ruins and artifacts, he possesses extensive knowledge of magic and of the various secret organizations that deal with magical phenomena, such as the Lion King Organization. His combat skills are centered on his expertise as a marksman; he prefers using firearms and has great skill with all kinds of guns. In particular, he can conjure various firearms from his coat, and these weapons possess anti-magic properties, including special bullets tailored to kill magical creatures.