eve of a festival; festival-eve vigil
Refers to the evening before the main day of a Shinto festival, often involving a smaller-scale celebration or vigil. Compare 宵祭り (よいまつり), which is a similar concept.
See also: 宵祭り (よいまつり)
On the eve of the festival, local people gather and hold a small Shinto ritual.
Tomorrow is the main festival, and tonight is the festival eve.
Standard kanji spelling for the eve of a festival, literally 'evening shrine'.
Alternate kanji spelling using 夜 (night) instead of 宵 (evening); less common but still encountered.
Compound of 宵 (よい, 'evening') and 宮 (みや, 'shrine'), referring to the evening before a shrine festival. The alternate spelling 夜宮 uses 夜 (よ, 'night') for the same reading.