If reviving the young girl Rion were treated as an engineering project,
with two major stages-"reviving her flesh and blood" and "cultivating her Demon Heart"-
then Li Xia had effectively outsourced the first stage to Sesshomaru.
This allowed both him and his ally to earn the Eastern Country's Great Demon King's goodwill and a favor.
That was how he had always treated good friends and allies.
As for Inuyasha?
Before Kagome chose him, he had actually felt rather despicable.
He had approached the girl as a classmate, then actively or passively disrupted the original storyline between her and Inuyasha. The two who should have ended up together in the Original Timeline had ultimately drifted further and further apart, while he and Kagome had fallen for each other and married instead.
Did he feel guilty?
Yes.
No matter how one looked at it, his appearance amounted to stealing someone else's love. Even if, at first, he had only wanted to grow stronger, had not joined the team with malicious intentions, and had not simply been using them or taking advantage of them, the fact remained that he and Kagome had ended up together. Inuyasha, by contrast, had missed out on the beautiful marriage that would have given him a happy ending.
Of course, that guilt faded after Inuyasha repeatedly acted like a fool and fell for Naraku's schemes.
He could not rest easy entrusting Kagome's safety to Inuyasha and Naraku's generosity; as for handing over the girl he loved from the bottom of his heart, wronging himself to respect the predetermined plot, that was even further beyond him!
What could he do? He was not that easygoing a man.
Most importantly, Kagome had fallen for him, and he had fallen for Kagome-very, very deeply at that.
That was enough.
Knowing how