You don't have to play as both ranger types if you don't want to. You could take one type then go with your Kamen Rider.

Name: Komori Rin
Gender: Female
Ranger: Black Justice Ranger

Name: Musashi Haruki
Gender: Male
Ranger: White Justice Ranger

Name: Kazuyoshi Kushi
Gender: Female
Ranger: Silver Justice Ranger

(Kushi will be the new/loner/young veteran Ranger in the story)

Name: Mizukawa Hirotaka
Gender: Male
Ranger: Crimson/Red Hoshi Ranger