You might want to start in Yokohama and walk north to Tamagawa Station. Then you won’t have the sun in your eyes so much. (That factor is more important to consider in the winter, though, when the sun is low and the sky is often very clear.)
Enjoy your walk! I did that route only once, and it might be the nicest one. My usual route was parallel to the Keihin Tohoku Line—Tsurumi, Kawasaki, Kamata, Omori, Shinagawa, etc. A bit industrial, but not bad on New Year’s Day.
There aren’t many possible routes because there are very few bridges over the Tama River.
