As we all know (cause manga/anime told us so) the japanese are extremely weak to water, wind and cold damage. Even a brief exposer to any of these damage types can cause a serious, potentially lethal debuff status. The fact that she was running on a cold day would have raised the wind shear, and she was crying so she was unknowingly taking water damage as well, compounding the problem. She's very lucky to be alive at all, I can only hope he'll except his confession before her tragic, untimely, and imminent death.