Overdrafted
Ryu felt completely drained. Using the last of his strength to summon Esme like that really felt like he was scraping the bottom of a barrel. He had truly hit his ceiling.
At the moment, though, Ryu was only glad that his plan had worked. Having to defeat those two while also making sure not to damage their futures was really a pain in the ass. His Grandpa Kukan was definitely right about women.
In the end, he had to wear them down until they had almost nothing left before catching them off guard. But, even then, he had relied on some of the special characteristics of Osiris.
Had Ryu teleported Esme and then had her attack, the two would have likely still reacted fast enough to dodge. And, by this point, Ryu didn't have enough energy left to control Esme in battle, so his fate would have been sealed.