Legacy of the Seven Stars arc

The Inheritance of the Seven Stars arc is the third story arc of the Black Bullet series.

After declaring war on Civil Security, Kagetane proceeds to the next phase of his plans: awakening the Stage V Zodiac Gastrea. Rentarō, Shōgen, and their Initiators ready to confront him as they enter an area unexplored by man, facing many challenges along the way.

Rentarō and Enju
Rapidly running and arriving to Enju's school, Rentarō hears the young kids around him speak poorly of her, leading him to suppress his emotions and run towards Enju. As he keeps running, more and more kids begin to talk about her and the fact that she is a Cursed Child, which causes him to remember all of the memories he shares with her; calling the kids at her school the real monsters. He finally reaches the crowd encompassing the young girl, hearing them throw insults at her whilst she tries to defend herself. Enju is thrown a bag as Mai comes by and sequentially ignores her. Before she can go after her, Rentarō appears behind her and stops her by holding her, and explaining to her that the kids at her school are no longer her friends. Weeping, she questions where she should go, but Rentarō gets a call from Kisara, whom tells him that they have sighted the Gastrea that infiltrated the Tokyo Area; telling him to go after it and retrieve the case. Before Rentarō can say anything, a helicopter appears above him, taking him and Enju to the Gastrea's whereabouts.

Aboard the helicopter, Rentarō sees a kite, but looking closely he notices that in fact it is the original Gastrea. He tells the man flying the helicopter to lower the altitude whilst following it. However, Enju opens the back door, shocking them both, and jumps out the door to attack the Gastrea. Shortly thereafter, Rentarō once again orders the pilot to lower the altitude as he lowers himself to the ground by a rope. Albeit, he slips and falls on his legs to reduce the impact. Injured, he gets up to see Enju confronting the Gastrea, and quickly defeating it with angered-filled attacks. Before she can continue her assault any further, Rentarō comes behind her and stops her. Enju then emotionally tells him that her only wish is to protect everyone in the Tokyo Area, which leads him to hold her tight and remind her that he is here and he thinks of her as family. After hugging, they see the case and get ready to retrieve it, but before they can, Kagetane and Kohina intervene. While Rentarō handles Kagetane, Enju faces against Kohina. But the opponents prove to be stronger as Rentarō asks Enju to leave and look for help. After she does, Kohina comes behind him and stabs him while insulting him. He moves away from her swords, but coming near a hill comes to a stop, turning around to see Kagetane pointing a gun at him and shooting him. Whilst Rentarō falls, Enju rushes thorough the forest looking for help.

Rentarō remembers the time he and Kisara were attacked by a Gastrea, leaving him at death's door. He wakes up when he remembers Kikunojō Tendō telling him to live, Enju and Kisara overhearing him scream in pain from the outside. They enter the room and Enju quickly jumps on him as Kisara welcomes him back and gets some food for him. Shortly afterwards, Kisara and Rentarō begin to converse and eat, making Enju jealous; interrupting them by telling Rentarō that she has something to show him. As soon as she leaves, Kisara reveals to Rentarō that Shōgen Ikuma is his savior, and that Kagetane's IP Rank is 134, leaving him speechless. Before they can continue, Kisara's phone rings, Seitenshi being the caller. She asks Kisara to put Rentarō on the phone, which she does. Seitenshi tells Rentarō that he must take part in the mission to take Kagetane down, but he refuses at first. When she readies to reveal something of great importance, Kisara closes her phone and tells Rentarō to go outside with her to get some fresh air.

Reaching the rooftop, Kisara explains to Rentarō the current situation, revealing that Kagetane's goal is to release a Stage V Gastrea, also known as the Zodiac Gastrea. Rentarō is left speechless, and just then, Enju comes to their location, angrily, showing Rentarō her bag and a letter that tells her to work hard that someone from school wrote; which gave her courage to keep fighting. Enju's words strike Rentarō, leading him to tell Kisara to inform Seitenshi that he will be joining the war. Before he leaves, however, Kisara begs him to stay safe. Rentarō arrives to Sumire's lab, where they speak about the past. Before he leaves, Sumire gives him a set of AGV Experimental Drugs and is told to use them only if in real danger. Enju and Rentarō arrive to the place of departure, seeing Kayo and Shōgen. Shōgen comes to their side and tells Rentarō to go home, but the teen denies and thanks him for saving his life. Blushing, Shōgen is pulled by Kayo, whilst the man insist on Rentarō going home, as they get ready to leave. Rentarō and Enju then ready for departure.

Entering the Unexplored Area
Rentarō and Enju arrive to the area unexplored by man, navigating thorough a dark cave. As they keep walking, trying to keep as quite as possible for a Gastrea not to notice them, Enju suddenly jumps on Rentarō and knocks him to the ground. Rentaro questions her motives, but she tells him to stay quiet; which he does after noticing the Stage IV Gastrea passing by them. As the Gastrea walks away, Rentarō thanks Enju for saving their lives and calls her a good girl, filling her with happiness. However, as they ready to leave, they hear an explosion nearby, turning towards it as they ponder what will happen next. Much to their misfortune, the Gastrea they previously avoided reappears, leading Rentarō to asks Enju if she can carry him and run as fast as she can, which she does. Running from the Gastrea, the two state that they trust one another. Enju seemingly outruns the Gastrea, but reaches a cliff. However, she solely gathers enough momentum to make a high jump. As they jump through the air, they see Heaven's Gate. Finally reaching the ground, Enju decides to take the lead but is stopped by a gun, turning out to be a wounded Kayo holding the object.

Target located: Kayo's identity
Enju stands on the other side of a wall while Rentarō tends to Kayo's injuries. After introducing herself, Kayo begins to speak to Rentarō about what happened prior to their encounter; revealing that she and Shōgen were the ones that caused the sudden explosion to go off earlier, claiming that a Gastrea sneaked up on her and, scared, she dropped an explosive. Rentarō begins to scold her for her actions, but sets it to the side as he ponders what Gastrea attacked them, briefly dictating the Gastrea's abilities being mixed with and  genes. He continues to claim that with the Rye genes the Gastrea is able to eject a pollen that attracts humans, leading him to conclude the reason for their downfall. Blushing, Kayo looks down and calls Rentarō a genius in biology, causing him to blush slightly and shadow the comment. After Kayo gets a good laugh out of his shyness, she reveals that she is a bit jealous of Enju. When Rentarō questions if she is happy to be Shōgen's initiator, she states that he views them as mere tools for killing.

Rentarō contradicts her statement, stating that they are human as well. Substantially, Kayo questions if Rentarō has ever killed anyone, which shocks him when she tells him that she has. Further; she states, Civil Security does not think twice before killing Gastrea similarly to how Sumiaki Okajima was killed. Rentarō pins Kayo to the ground, telling her that the Cursed Children are not monster, but she claims that his words are filled with pity. However, she does not wish to deny them as she calls him righteous. Getting off of her, they continue to talk about the Cursed Children and the project that took place several years back, Kayo pointing to Heaven's Gate. Suddenly, she gets a call from Shōgen, who tells her that they have located Kagetane and Kohina.

When they arrive to the location, they are quickly attacked by several Gastrea, but Kayo rapidly handles them all using cogitation, shocking both Enju and Rentarō. She then reveals that she is model Dolphin.