Get off at JR Ofuna Station (Tokaido Line/Yokosuka Line/Keihin-Tohoku Line).
Take a bus from Nishiguchi (West Exit) Terminal, JR Ofuna Station. Take either the bus for the destination "Totsuka Bus Center" or "Matano Koen/Yokohama Yakkadai-mae". Get off at "Miyanomae" bus stop (approx. 5-minute ride). From there it is an approx. 2-minute walk to the Yokohama Plant.
Alternatively, from the same terminal, take the bus for the destination "Sumitomo Denko Junkan". Get off at "Nikon-mae" bus stop (approx. 6-minute ride).
*Only available weekday mornings up to around the start of office hours.