How could he be expected to do nothing?
Every day for months on end, Kanba had to watch Himari suffer. He had to watch her lay in her hospital bed, looking so small and frail; some days she wasn't even able to lift her head. He had to see the expression that painted her face on her worst days – eyes squeezed shut, contorted in pain, yet still trying to muster up a smile for his benefit. He had to watch her look out the window longingly, listen to her asking him softly how the weather is outside or how his day at school was. He watched her fade from the vibrant, gentle girl she was into a colorless, skinny shell of a person.
"Hey Kan-chan. If I ever get out of the hospital, we should do something fun together." She said wistfully one day, while half-heartedly flipping through a magazine.
"If? You mean when." Kanba replied, though to his ears, it sounded like more of a plea than any reassurance. He hoped she didn't notice. "You'll definitely be cured and then we'll do something fun together. I promise."
It was a helpless feeling. All he could do was clutch her hand – hold it tightly as though it would somehow protect her from the disease, prevent her from leaving him alone in the world. All he could do was keep her company and tell her stories and put on a brave face, because he knew that if he broke down crying in front of her it would only upset her. He couldn't even allow himself to cry at home, because he couldn't let Shouma see. He had to be strong for his family, for her sake.
But how could he be strong when he couldn't do anything to help her? Kanba couldn't save the girl who had become his most precious person, no matter how many empty promises he made to her. He could pay for her room, and for the best doctors, and for whatever treatment she needed…he didn't care what he needed to do for the money… but none of that was enough. She was incurable. In the end, despite all his effort, he couldn't do anything but watch her waste away.
So was it any wonder that when a miracle happened, he clung to it like a dying man? His sister had died and yet she was smiling and laughing and looking healthier than she had in such a long time. She was finally able to leave that horrible hospital. It was wonderful and Kanba only wished he could enjoy seeing her so happy. But the miracle came with a price. As amazing as it was, it was frightening at the same time – frightening because her life was still hanging precariously in the balance. This small happiness that they had been allowed could be snatched from them at any time – something he had already witnessed three times when Himari had close calls.
It wasn't going to happen. He wasn't going to let Himari suffer like that ever again. Kanba knew he wouldn't be able to survive watching her wasting away in that hospital bed again, especially not now when she was enjoying her life so much. But he wasn't powerless this time - he could do something. He could search for the "penguindrum." He could pay for the medicine that was keeping her alive. He would do anything for her sake, to save her. If it cost him his own life, then that was a small price to pay. Because more than anything – he loved her.