Little by little, Yoite has been losing his senses as his body shuts down, but he's also been losing the wall that holds in all the emotions he's been hiding--even from himself. And Miharu's not the only one who notices, nor is he the only one who cares.
Clearly, Yoite doesn't understand the full scope of his influence on the lives of those around him. But all those worried glances in his direction aren't about what terrible thing he might be planning to do to the world at large--they're about what he might be planning to do himself. And the more he unconsciously reveals to Miharu, the more the latter questions his promise to make it all go away--and the more the reader wants him to question it. So good.