In phenomena occurring in nature and in society, it is often commented that “Something may happen at any time, but it is difficult to predict when that something may occur.” Solar flares, volcanic eruptions, extreme rainfall, and economic crises are examples of this. Such cases are called sudden phenomena. Prediction of sudden phenomena is one of the important issues in physics. By comparing physical processes related to sudden phenomena by researchers from various fields, new research is being initiated in which we fully understand sudden phenomena and what we understand leads to predictions of those phenomena.