Although the Spider Brother and Spider Sister had no idea what had just happened to the Spider Princess, they could sense that she was no longer the timid figure they once knew.
The display of strength she had just shown was enough to effortlessly kill the Spider Father—the strongest of the Spider Family after Rui. With such power, she could even challenge Rui himself. If they aligned with her, perhaps they could finally escape Rui's oppressive control.
It wasn't just the Spider Princess; every member of the Spider Family was weary of this so-called "family game." But Rui's overwhelming strength had kept them in line.
And compared to the unpredictable and cruel Rui, the Spider Brother and Spider Sister felt that the once-timid Spider Princess might be easier to reason with.
Tanjiro and the others, who had already subdued the Spider Brother, suddenly became alert when they heard the two demons calling the Spider Princess "Mom."
Tanjiro had already dismissed any doubts about her after witnessing her transformation. The aura she exuded now—the scent, the presence—it reminded him of her brother, Ren Kuroda. But hearing those two young demons addressing her as "Mom" made him pause.
If she had lied, the situation could be catastrophic; she was clearly stronger than the large spider demon they had just faced.
If it was true, though… Tanjiro could only admire Ren's skill. The half-demon had even managed to win the loyalty of the mother of two children. Judging by the apparent age of those demons, it was almost like he was about to become a father unexpectedly.
"Shut up! I'm not your mother. This was just a fake family game. You didn't take it seriously, did you? And while I didn't go as far as that guy on the ground, you two aren't exactly good people either."
The Spider Princess's voice was cold, merciless. She launched several strands of silk at the Spider Brother and Spider Sister, piercing their bodies. The paralyzing toxin coursed through them instantly, forcing them to collapse to the ground.
Without a Nichirin Blade, she couldn't fully eliminate them—she could only paralyze them, leaving the finishing blow to Tanjiro and his companions.
Her ruthlessness wasn't just born from disappointment in this so-called "family." It was also selfish.
Ren had said he wouldn't transform other demons—who could be certain? Her brother might be ugly, even as a demon, and male, so probably not interesting to her master. But her sister… beautiful and potentially catching her master's attention? Spider Princess couldn't risk it. She had to nip that possibility in the bud.
Perhaps even she hadn't realized it, but after becoming a demon, she had developed a touch of yandere tendencies.
Meanwhile, Tanjiro, having freed the Spider Father from his suffering, looked at the Spider Princess now returned to her human form. He swallowed hard, instinctively deciding that staying close to her might be dangerous.
She appeared calm, gentle, even serene—but after witnessing the state she had inflicted on the Spider Father, he couldn't trust that demeanor. Just like with Ren before, once battle began, their usual personalities seemed entirely unreliable.
Not far away, while Tanjiro and his companions handled the other members of the Spider Family, Ren finally saw their main target:
Rui—the spider demon who was one of the Lower Rank Five demons of the Twelve Demon Moons.
He appeared as a short white-haired boy, indistinguishable from the Spider Family, playing the role of the youngest child within the household. But in reality, he was the strongest member of the Spider Family. Most others had gathered under duress, either fearing the Demon Slayer Corps or Rui himself. Only Rui truly enjoyed playing "house."
Perhaps because Rui's childhood mirrored, in some ways, the experiences of Muzan Kibutsuji, the Demon King's tolerance for him far exceeded that of the other demons. Rui was allowed to act however he wished on Mount Natagumo. Though he looked like a child, his age stopped progressing after becoming a demon, leaving his true lifespan unknown.
"It seems you are one of the so-called Twelve Demon Moons. Normally, killing children would weigh on my conscience. But since you are a demon, I doubt your age matches your appearance."
Ren eyed the boy-like Rui warily, surprised that the ultimate boss of Mount Natagumo was disguised as a child.
"My useless family members never did their duty as parents or older siblings. Fine. After I kill you, I'll take care of them too—and then I'll find a new family."
Rui, however, was furious—not just at Ren's intrusion into Mount Natagumo, but at his own "family." They had failed to protect him again, letting an outsider appear before him. Though he was the strongest demon in the family and a member of the Twelve Demon Moons, Rui, playing the role of the "youngest child," craved protection. His family had failed him once again, and he seethed with rage.
Rui had a twisted obsession with family bonds: parents should protect children, older siblings should protect younger siblings, even at the cost of their lives.
Ren's cold and indifferent words immediately dispelled any lingering guilt. He, too, had family—his mischievous sister, their forgetful yet nagging mother—and they were irreplaceable treasures.
"So, in your eyes, family is something replaceable? You, who so desperately crave the protection of your family, have you ever considered that kinship isn't one-sided? That strength should be used to protect them, too?"