There is a simple solution to all of this. Instead of her learning how to open the space up, he should work on his training and get stronger. If he does, then he won't feel so drained.
'I have been slacking on using my hanyou abilities and my flames since meeting Sumire. I knew about her memory loss; she forgot about herself being a hanyou and an evolved human. I didn't want to overwhelm her with too much.'
For him, what was the most important was making sure she healed. To make sure she could smile again. Now that she can finally smile naturally, he can return to what he did before she came.
Return to the days when he would train daily to strengthen these monstrous powers inside him.
His thoughts break off when Ran sits down beside him. At first, neither of them said anything but then Ran spoke up.
"So, do you two do that often?"
At those words, Yuhi coughed. "Not often, just recently."