shall i need tourist visa? is there any entrance port in zhujiang

i am japanese and japan passport holder. i want to go from hongkong to guangdong area(zhuhai,zhongshan,doumen or jiangmen) by ferry. after immigration i want to go west(yangjiang,hepu and dongxing) to vietnam by bicycle. i will travel 10 days in china. shall i need tourist visa? and which port am i allowed to enter in?