Kamen Rider ganbarider: Multiverse crossing

A kid with a dream to be like his own Heroes and save the day, but his dream and life were swept away on the fateful night he lost his family. Years later as a call from an old friend came, offering hi ma chance to be what he dream of becoming when he was younger, and be a Kamen rider.

As a evil man stolen something of guy's father's work, he is task to travel the multiverse, help out every world he comes to, seek out the one responsible, and take back what the villain had stolen, while his journey he meet few friend, gain a new family, and many lovers along the way.

Massive Harem story.