Kaizen philosophy focus on productive improvement in production process whereas circular economy talks about sustainable waste management. CE cover waste management at all levels by applying 3R principle i.e. Reduce, reuse and recycle or up-cycle.
To me, Kaizen philosophy is positive and circular economy is negative, kind of like the yin and yang. Kaizen philosophy attempts to improve production, while circular economy attempts to eradicate waste. The two work symbiotically, such that each presupposes the other.