Per the answer given to Ignis's question above, we might have a solution for you!

Characters who have arrived with chronic illness or other issues, such as blindness caused by damage in their world, cannot regain their health or sight permanently. However, they may be able to regain these things for a short time, spanning the duration of the event. In this instance, Eichi might be able to live "free" of his illness from the 16th until the 20th.