Protagonists
Main
Yajuko (Beast Child)/Rock/The Black Rock Shooter (gains her mother's sword and has her pistol enhanced by her older sister, BRS Beast's weapons)
Ron (A talking horse/pegasus)
Elder Caster (BRS's older sister)
Major Allies
Strength
Black Matagi (BRS's childhood rival)
Minor Allies
Yomi (Dead Master's younger sister)
Yuu (Strength's twin sister)
Mato (BRS's younger sister)
Dragon Slayer (BRS's mother)
Antagonists
Grunts
Farside Bunny
Loveness
Tightmare Elly
Chariot (BGS's cavalry commander, later becomes an ally)
Elites
Dead Master (BRS's main rival, BGS's most paid assassin)
Saya Irino/Black Devil Girl (BGS's first lieutenant and sole child)
Infinite Range Maid (BGS's second lieutenant and personal maid)
Main
Black Gold Saw (corrupt monarch, sister of DS, aunt of BRS, Caster, and Mato)
Mato as White Rock Shooter (sort of)
Plot
Part 1
1: Story begins with Rock waking up from a nightmare, reminded of her village's decimation and Mato's capture a couple months ago, as well as her mother's disappearance. She then goes to train with Elder Caster, before successfully preventing a raid on their recovering village.
2: Rock and Caster eventually travel to try and find Mato and their mother. Soon, they encounter Black Matagi, who's in a battle with Dead Master. After forcing DM to retreat, they arrive at the neighboring village, greeted and sheltered by Yomi. DM follows to attack, before retreating upon spotting Yomi.
3: BM explains that she will stay in the town until she's properly recovered, before bidding farewell. Eventually, Caster and Rock make it to the next village, getting into a brief skirmish with the guard Strength. Eventually, Yuu arrives and drags them all into her home, apologizing for Strength's behavior and explaining that she's overprotective of her home.
4: In compensation for the injuries Strength gave, she lends Rock and Caster a steed named Ron. Rock and Caster accept the gesture, assuming that Ron is a normal horse. During their travel to the next village, they are ambushed by DM and are immediately saved by Ron, who flies towards the next village, revealing that he is a pegasus.
5: After spending time in the village to recover, Chariot arrives with her cavalry to invade the surrounding villages, as they are the last bit of territory left for Empress Black Gold Saw to conquer. Strength and BM arrive and help Rock and Caster liberate the villages, before DM injures Chariot, explaining that she herself will be the one to kill Rock.
6: After successfully liberating the villages, BM agrees to keep watch on her and Rock's respective home villages. Strength returns home, while Chariot is left to heal and be humbled, and realize her mistakes in serving BGS.
Part 2
1: Rock and Caster eventually travel to the southern towns, steadily liberating them one by one, before encountering the general Tightmare Elly. The two easily take her down, before being interrupted by a dragon spotted overhead. Instead of attacking, the dragon merely takes TE as its meal and leaves in a hurry, leaving Rock, Caster, and Ron stunned.
2: The sister duo then reach the western towns, finally finding the first real clue to Mato's potential location. After liberating the towns, they encounter Loveness, who claims that she knows where Mato is and will only give information for a price. Unlike Caster, Rock falls for the general's trap, before going into a rage and brutally killing her. She is forcefully sedated by Caster, who's realizing how powerful Rock's becoming.
3: After Rock wakes up, she and Caster are already in the eastern towns. Ron explains what's happened, saying that BM and Strength are helping her sister, and questions Rock if she remembers anything during her rage. Rock confirms that she doesn't remember, before receiving a visit from Yuu and Yomi. Rock explains what she's been going through and begins to doubt herself.
4: Caster returns with some shocking news. Much to everyone's shock, a confused and scared Mato is behind her, to which she explains that while it might be Mato, someone has magically tampered with her. Yomi and Yuu suggest that Mato should stay with one of them for her own safety, before the group is interrupted by Farside Bunny's invasion to the north.
5: Rock, Caster, BM, and Strength encounter FB in the northern towns, who demands Mato in exchange for the towns' safety. They deny her demands and an all-out battle ensues. Chariot eventually arrives and help give the four the edge they need to defeat FB. Once again, DM appears out of nowhere to help for her own interests. Before Rock and Caster can question the general why BGS needs Mato, FB poisons herself to retain information.
6: Rock and Caster are eventually convinced to bring Mato along. The rest of the group joins them and so far, everything goes well, before the dragon appears again, this time out of control and desperate. The group attempt to flee, with Caster and Rock providing distraction, only for Rock to be taken out and captured by the dragon. Caster tells the group to head to the cities and stay low while she searches for Rock.
Part 3
1: Rock wakes up in a small camp, before noticing the last person she expects. Her own mother, Dragon Slayer. DS explains what happened to her, causing her daughter to notice serious injuries on her abdomen. DS reassures her that she'll heal fully soon, after how she helped her.
2: Rock and DS chat and train, helping Rock get into touch with her new strength and to control her more wild instincts. DS then reveals a shock; she is the very dragon that's been following her daughters, but now, she's losing control. Despite her mother's wishes, Rock insists on helping.
3: DS, for the time being, remains in control and explains that they are running out of time. Soon, Caster (along with Ron) finds them, also suffering from an aliment (a type of cancer that targets only pure mages). The family members don't know what to do, so DS lends Rock her sword, telling her how proud she is of her daughters before leaving and transforming into the dragon in private.
4: Rock and Caster feel more lost than ever, now that their mother is truly gone. Caster attempts to enhance Rock's gun and their mother's sword for Rock's personal use. Eventually, Rock finds herself more attuned to her powers than ever, but still lacks control. Eventually, DS in dragon form arrives and attacks them.
5: The two try to keep the fight away from the city with little success. Eventually, Rock finds herself losing control, as she's essentially in a position where she has to put down her own mother…and she can't do it. Caster lends Rock her supplies and urges Ron to take Rock to the group, which he reluctantly does…all while Rock is forced to watch the dragon devour Caster whole.
6: Now inside the dragon, Caster makes her way to the organ where her mother is trapped. DS apologizes to her for her daughters' fates, letting her eldest daughter hug her as the entire dragon is destroyed from the inside out. Rock is at her lowest point, angry at herself for being too weak. The first vestiges of Beast come out. Ron then urges her to continue on, as while she lost Caster and her mother, Mato is still safe and waiting for her.
Rock and Ron then go into brief solitude, so Rock may train, refine, and master her power.
Part 4
1: One long year after starting her journey…and only a few months after going into solitude, Rock and Ron head to the city. They manage to get to an inn where Yomi and Yuu are working and explain where they've been. Yomi and Yuu, heartbroken by the loss of Caster, explain that the group has gone into hiding to avoid capture.
2: Rock and Ron take on small jobs to help Yomi and Yuu out, before encountering a disguised BM and Strength, who are rightful pissed by Rock's sudden disappearance. They get into a fight, which only ends after Rock confirms Caster's fate. Strength leaves in fury, while BM can only cry in Rock's arm over the loss of a person they both cared for.
3: BM brings Rock to Mato, who's become more and more void of emotion. Rock explains what happened with a heavy heart, while Mato explains that ever since she came to the city, she's felt more empty than ever. Rock counters this that, despite that, Mato is more honest than ever. Rock then makes it her mission to stop BGS's reign and to restore Mato.
4: Rock is then threatened by DM to meet her in the city's cemetery. Before going, Yomi tells her the truth about her and DM. Rock can't promise that DM will be saved from herself, but at least she can free her of this life. And so, Rock and DM have their fated duel, which lasts until the next sunrise and ends with DM's death.
Not at Rock's hands, but by Saya Irino.
5: Rock is then convinced by BM to train with Chariot, who has been gathering a rebellion to help stop BGS. Chariot and Rock train, once again revealing vestiges of Beast as Rock's determination grows. Chariot then notices that Ron has also gotten stronger, noting that he will need it for the battle.
6: Eventually, the group is ready the storm the castle, having evacuated most of the civilians. So, the rebellion charges into the city, with Rock and Mato immediately heading towards the castle for answers.
Part 5
1: Chariot and Strength deal with the cavalry, lead by Saya Irino. Not much to go here, since it is just a fight.
2: Upon entering the castle, BM deals with Infinite Range Maid alone so Mato and Rock can get to BGS uninterrupted.
3: Mato and Ron are split from Rock by BGS, forcing Rock to fight the queen alone. It is a long and grueling duel, which ultimately has BGS drop the bombshell that Rock, Mato, and Caster are her nieces. In response, Rock merely laughs and says that it is destiny for her to overthrow their aunt, before finally transforming in BRS Beast. She defeats BGS, who then merges with her castle to give her an edge.
4: Rock and BM are launched from the castle, now transformed into a golem in BGS's likeness, before noticing Ron breaking free with Mato and rushing to Rock's aid. Another long fight ensues, before the golem is left defenseless. Rock has Ron escape with BM, before she and Mato venture into the golem's body in search of BGS's true body to kill it.
5: Upon entering the organ where BGS's body lies, White Rock Shooter steps forth and fights Rock, claiming to be the true Mato. Mato is in heavy pain, believing this to be true, but can also tell that WRS is also not whole either. Rock eventually restrains them at Mato's wish, before using Caster's supplies to figure out the problem.
Eventually, Rock determines that WRS is a product of BGS's forces experimenting on Mato.
6: Rock and WRS fight, before WRS is killed via her own arrogance, plunging into the magma surrounding them. As Mato begins to feel whole again, Rock prepares a bomb to take out BGS, before the two sisters attempt to leave…only for BGS to seal the golem up, saying that if she's going to die, she'll take her traitor of a sister's children with her. Ron then breaks in, before escaping with Mato and Rock.
Not sure what the epilogue might be. While BGS is dead, I don't think Rock or Mato would willingly become the next monarchs, despite both fulfilling the requirements as proper heirs. Admittedly, I think Rock would take up the mantle of queen, just so the kingdom doesn't fall into chaos or get conquered.