Another theory says that it is derived from an idea that the emperor is a descendent of Taiyoshin (the sun god), i.e., 'demise of the emperor means that the sun hides behind a cloud'.
天皇が太陽神の子孫であるという思想、すなわち「天皇の死去＝太陽が雲に隠れる」から来ているともされる。