The Moonlit Legend: Reborn(Kamen Rider Kuuga X Sailor Moon)

Centuries ago, The Earth and Moon Kingdoms were under the attack of insectoid creatures known as Grongi, bent on bringing forth the ultimate darkness.
Many tried to stop them, but it was in vain.
until a masked warrior of the Lynto tribe known as Kuuga defeated them all, and sealed them away at the cost of his life.

In the present day, a young boy by the name Iron Onodera lives out a normal life in Tokyo, that is until he comes across a stone relic of some kind.
but what he didn't know is that ancient relic was more than what it seemed...