bloody, smelling of fish, raw smelling
腥 centers on a strong, unpleasant raw smell, especially the metallic scent of blood or the fishy odor of raw seafood.
腥 combines ⺼ (flesh/meat) with 星, which likely contributes the sound and may suggest a raw, bloody quality associated with fresh meat or fish.
The flesh radical ⺼ beside 星 (star) suggests raw meat or fish left out under the stars, becoming bloody and smelly.
For セイ, imagine saying 'say' to the raw, smelly fish: 'Say, that's bloody!' The word 'say' cues セイ while the scene reinforces the raw smell.