Both are about washed up musicians who now host a radio show...when the daughter(s) they never knew they had show up to live with them.

Same director using the same quirky style. However Memories of Matsuko has a much darker plot.

Both movies are about parents looking for their kidnapped son in China.

In both dramas a baby is left with multiple men who could possibly be the biological father and take care of the child together.

Both dramas are about a mermaid/merman and human falling in love.