Episode 1: Kamen Rider Kabuto

The implication: His sister was lost in the Worm attack 7 years ago (or was taken by ZECT?).

Satoshi Tenma, a young man with a mysterious past, returns to Japan after years abroad. Simultaneously, humanoid creatures called Worms—alien lifeforms that mimic humans—begin covertly infiltrating society. After a series of violent Worm attacks, Satoshi discovers he is connected to the Kabuto Zecter, which transforms him into Kamen Rider Kabuto. He intervenes to stop a Worm assault, confronting both human and Worm adversaries and beginning his journey as a Rider while uncovering hints about his lost family and suppressed memories.

The implication: His sister was lost in the Worm attack 7 years ago (or was taken by ZECT?).

Satoshi Tenma, a young man with a mysterious past, returns to Japan after years abroad. Simultaneously, humanoid creatures called Worms—alien lifeforms that mimic humans—begin covertly infiltrating society. After a series of violent Worm attacks, Satoshi discovers he is connected to the Kabuto Zecter, which transforms him into Kamen Rider Kabuto. He intervenes to stop a Worm assault, confronting both human and Worm adversaries and beginning his journey as a Rider while uncovering hints about his lost family and suppressed memories.