dishes seasoned with vinegar or miso
齏 centers on dishes that are dressed or seasoned with vinegar or miso, typically finely chopped or mashed ingredients mixed with a tangy sauce.
齏 combines 韭 (leek) with 齊, which likely contributes the sound and possibly the idea of mixing or arranging. The character originally referred to finely chopped leeks or vegetables seasoned with vinegar or miso.
The outer 齊 suggests something arranged or mixed, and the inner 韭 is a leek. Picture finely chopped leeks being mixed with vinegar and miso to make a seasoned dish.
For セイ, imagine saying 'say' as you offer someone a seasoned dish: 'Say' -> セイ, and they taste the tangy vinegar-miso flavor.