William Lee Rand, Usui Reiki Master Lineage, answered my question about the meaning of The Logo of Reiki which looks very similar to a Magen David:
The Japanese kanji in the center of the logo means Reiki which is spiritually guided life energy. The upward pointing triangle represents humanity moving toward God. The downward pointing triangle represents God moving toward humanity. Because the two triangles are united, and balanced, they represent humanity and God working together in harmony. The inner sixteen petaled flower symbolizes the throat chakra or communication. The outer twelve petaled flower symbolizes the heart chakra or love. The complete logo represents Reiki uniting God and humanity in harmony through the communication of love.
The Logo is the Registered Service Mark of The International Center for Reiki Training.