This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
膎 combines the flesh radical ⺼ with 奚, but the exact historical development is uncertain. It may have originally referred to a type of meat or preserved food, but this is speculative.
The left side ⺼ suggests flesh or meat, and the right side 奚 looks like a hand holding something. Imagine a piece of dried meat being held, but the exact meaning is unclear.
For カイ, picture a piece of dried meat being offered to a Kai (a person named Kai): Kai -> カイ, and the meat is held out.