The rendering from both lenses are amazing and in fact full of character...
The Chiyoko 5cm f2 is a 7 elements/ 4 groups, following summitar design, throws out high contrast images in bnw and my copy seems to rendered swirly bokeh when shot at f2.
The Nikkor 5cm f2 has 6 elements/ 3 groups, single coated, it was believed to be a planar design lens..
This lens is a great lens for portrait, soft and glowy...(not as bad as the signature glow from the f1.4 lens)
As the market get quieter, these 2 lens are not too difficult to search for at a reasonable price.