Regarding why he wanted to save Kikyo: first, it was because her love with Inuyasha had a significant impact on the latter half of this half-demon's life.
After Kagome passed away, Inuyasha's emotional trauma erupted, and his strength stagnated completely, leading to his failure to survive the great demon catastrophe back then.
Second, since the system-'Jaken'-had the ability to resurrect one figure from the Demon Realm, he might as well use it.
Leaving it unused would be a waste.
After comprehensive consideration, Kikyo was the optimal choice.
Arriving outside the dilapidated village, Ray deliberately released a faint aura.
As the strongest priestess among humans, Kikyo naturally sensed the presence of this powerful demon.
She soothed the children who were playfully clinging to her, then made her way toward the hill outside the village.
"Inuyasha's brother, what brings you here to seek me out intentionally?"
Ray gazed calmly at the priestess who looked exactly like Kagome but had a completely different personality, offering no specific response.
Instead, he spoke to the Jaken soul behind him.
"Give it to her."
"Understood, Sesshomaru-sama."
The power of the system manifested, and a pale blue energy surged deep into Kikyo's soul.
Afterward, Ray had 'Jaken soul' dissipate on the spot, returning to the system.
Without another word to Kikyo, he turned and flew toward the valley where Inuyasha and the others were.
Kikyo frowned slightly, watching the direction Ray had left while lost in thought.
'What was that pale blue energy?'
It felt as if her soul had connected to some other world.
Yet, it had no effect on her current body.
Moreover, judging by Sesshomaru's attitude, Kikyo sensed no hostility whatsoever.
It felt more like an act of charity.
'Did Inuyasha ask him to bring me a gift? Hah, I, have no need for the pity of your dog demon clan.'
With that thought, Kikyo turned and headed back to the village.
She needed to settle the children for their rest, and later, she would go investigate the distant place where evil energy ran rampant.
Perhaps she could find traces of Naraku there.
...
Early the next morning, Kagome, Sango, Miroku, Rin, Jaken, and the others woke up one after another.
The group was somewhat puzzled: where had Ray and Inuyasha gone?
After a brief search, they found a hastily scrawled note at the cave entrance.
The messy handwriting was unmistakably Inuyasha's.
["We're off to deal with Sounga. Don't follow us."]
Reading this, Kagome couldn't help but fume.
'When has Inuyasha ever managed to solve anything on his own without relying on us?'
'Think you're all high and mighty just because you're going with your brother?'
'Hmm... with Ray around, it did seem like they weren't as necessary.'
But Kagome was still deeply worried about Inuyasha.
After discussing it, the group decided to set out for the evil-tainted city where Sounga was wreaking havoc.
Led by the elders, everyone mounted the two flying yokai—Kirara and A-Un—and headed into the distance.
...
Two hundred kilometers away, in a long-abandoned city spanning five kilometers, the area was filled with dilapidated houses and shattered marble pavements.
Logically, such a place should be devoid of humans.
But today, it was unusually different.
Nearly 50,000 undead soldiers had emerged from the earth, clad in armor and wielding decayed blades, spears, axes, and shields.
Their faces were withered, yet they stood straight.
All the undead warriors were gazing up at the figure standing high above: a headless, bizarre humanoid creature.
This humanoid figure held a slender demon blade with a red gem embedded at the end of its hilt—none other than Sounga.
The previous night, Sounga had located the grave of Inu Taisho's love rival, Setsuna no Takemaru, unleashed its power to resurrect him, and attached the left arm of Sesshomaru it had acquired.
Through Sesshomaru's arm, Setsuna no Takemaru wielded Sounga.
Under the control of the sword's spirit, he slaughtered incessantly.
Any human or yokai killed by Sounga would become a vengeful spirit under the demon blade's command.
After a night of carnage, he fully restored Sounga's Demonic Power and summoned a massive army of vengeful spirits.
Fifty thousand in total, awaiting the arrival of Sesshomaru and Inuyasha.
Unfortunately, once Sounga regained its full power, it promptly abandoned him.
Setsuna no Takemaru's lingering human consciousness hindered Sounga from unleashing its complete strength.
Thus, after discarding Setsuna no Takemaru, Sounga fashioned its own physical form to wield itself.
Only with the sword spirit in direct control could Sounga exhibit its full might.
This was the only way it could kill the two sons of Inu Taisho and transform the Demon Realm into a netherworld overrun by the dead.
The power of death was what Sounga cherished most.
...
Half an hour later, Ray and Inuyasha had arrived at the scene.
The dog-boy had been unceremoniously hauled through the air by Ray's Light Whip during the flight.
This left Inuyasha utterly humiliated and furious.
Upon landing, he immediately began berating Ray.
"You've gone too far! Even Jaken gets to grab your tail, so why do I have to be dragged by this whip?"
Ray shot Inuyasha a glare in response.
"Stop complaining. Focus on the task."
"Hmph, I can handle this alone. Just watch."
With that, Inuyasha drew Tessaiga from his waist and charged toward the fifty thousand vengeful spirits below.
"Wind Scar!"
A terrifying golden light instantly swept across a three-hundred-meter radius ahead, and thousands of vengeful spirits were shattered into fragments.
Ray frowned slightly upon seeing this; Inuyasha's Wind Scar seemed weaker than he expect.
The dog-boy, however, felt no such concern, convinced his strike was impressively executed.
Taking advantage of the gap torn through the army by the Wind Scar, he plunged deep into their ranks.
Just as he channeled his Demonic Power to unleash another Wind Scar, the thousand vengeful soldiers behind him abruptly regenerated.
Their shattered bodies reassembled, eyes glowing with an eerie emerald light.
In mere moments, Inuyasha found himself surrounded by an overwhelming sea of enemies.
These vengeful soldiers were remarkably powerful, roughly on par with elite marines from the pirate world.
Moreover, empowered by Sounga's energy, they could regenerate indefinitely.
Had they been deployed in a war, they would have been an immense asset.
This demonstrated how Sounga alone could rival an overwhelmingly powerful army.
It was precisely why Ray was determined to obtain it: for the sake of convenience.
But the immediate priority was to wrap up this battle alongside his foolish younger brother.
As for the method...
Ray flashed forward, hovering between Inuyasha and the distant Sounga.
He glanced at Inuyasha and drew Tokijin from his waist.
'Soryuha.'
It was a scaled-down version, at one-third of its full power.
A hundred-meter-long blue dragon roared as it surged toward Inuyasha, incidentally scattering the vengeful soldiers in his path.
Witnessing this scene, Inuyasha couldn't help but marvel inwardly, 'Damn, Ray. This coordination feels incredible in battle.'
Without another word, Inuyasha raised Tessaiga and swung it directly at the demonic energy vortex of the Soryuha.
"Bakuryuha!"
A kilometer-high tornado formed, charging straight into the city's interior.
The raging tornado swept through everything in its path, tearing nearly ten thousand spectral soldiers to shreds.
Seeing this, Ray immediately lashed out with another Light Whip, pulling Inuyasha as they flew deeper into the city.