This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
璯 combines 王 (jade) with 會, which likely contributes the sound. The exact historical development is uncertain.
The left side 王 suggests jade or a precious stone, and the right side 會 looks like a gathering. Imagine a gathering of jade ornaments, but the exact meaning is unclear.
For カイ, picture a gathering of jade ornaments shaped like a kite: kite -> カイ, and the jade pieces come together.