No matter what Yelen tried, Eren's body kept rejecting her essence. Even though she was his Guardian Spirit, her essence didn't appear to be compatible with his own.
Even if her essence was compatible, she should still be able to heal an ordinary person as her essence was pure. Only something even purer and more species could force her essence out when she gave it her all.
There was something inside Eren's body that didn't appear to like outside interference, treating every foreign essence as poison. That was the case unless it was forcefully snatched by Eren in the first place.
The only good thing about this situation was that Eren's breathing had soon stabilized even without her interference. She didn't know what caused him to be hurt in the first place, but his body being stabilized was even more strange.
"I'm the one who is hurt. Why do you look like you're the one in pain."
