Sidenote: I am seriously planning to make the title a pun. Enter Sandman anyone?
This is Kamen Rider Skull's henshin and fight sequence in the Kamen Rider W X Kamen Rider Decade: Movie Wars 2010 movie's second segment, Begin's Night.
As seen on this scene, Shotaro hasn't revealed to Akiko that his father is dead AND a Kamen Rider!