Making some guesswork here.
Spoiler: srsly, don't do it
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Shaya, depending on how used to interacting with powerful spiritual beings, may be overwhelmed by what she feels from Katsuo's 'heart'. There is a phenomenal well of strength, both existent and potential, behind the quiet, nervous boy. Something that he probably doesn't even know he could tap, that he could grow into at almost any time he was ready. Despite his lack of true spiritual pressure like most beings are capable of letting off, it is almost crushingly amazing. And yet uplifting in that way Katsuo has mastered.
...and yet, there was a point of worry. Even though his chain is not visible, Shaya may be able to feel that it is damaged in some way. Perhaps the links aren't broken, but they are cracked and bent out of place. That in all honesty, Katsuo probably should be dead. Or worse. And of course, for all his inspirational heart and strength, he could truly be terrifying if his chain were to break...