Of course, Hyuga Kagami did not need Shion to revive him. He said that only to give her some motivation, because he knew very well that what Shion lacked was not ability, but motivation!
As long as she had strong enough motivation, courage would naturally follow.
And even aside from Hyuga Kagami's personal interests, this truly was the best time for Shion—or rather, the Miko of the Land of Demons—to deal with the dark side known as "Moryo."
Even while sealed, Shion had been the strongest Miko in history when it came to clearly seeing the "Death Prophecy."
The essence of the "Death Prophecy" was an advanced application of a Miko's own Miko power, so a sealed Miko should not have possessed this ability at all.
The fact that Shion could unconsciously use the "Death Prophecy" while sealed proved only one thing: the seal placed by the previous Miko, Shion's mother, could not completely suppress even Shion before she had turned ten. After all, Shion had already activated a "Death Prophecy" several years ago, when Akatsuki first attacked Konoha.
So if even Shion could not resolve the problem of "Moryo," then the chances of future Miko successfully dealing with "Moryo" would be even lower.
For all these reasons, whether for public or private interests, Hyuga Kagami had to encourage Shion to bravely give it a try.
"Fine, I'll try!"
After learning that resolving "Moryo" could revive Hyuga Kagami, Shion did not hesitate for long before gritting her teeth and nodding.
Seeing that Shion was still full of fear, Hyuga Kagami smiled. "Don't worry. I'm here!"
With the Giant Tenseigan, he could extract chakra. So even if something went wrong while Shion fused with "Moryo," allowing "Moryo" to seize the initiative during the fusion, he could forcibly extract "Moryo" from Shion's