Kamen Rider 21

It's a similar process to the other Den-Os, although with different armor on the body of course and it's a police car-looking thing that drives down his head and forms his mask. It's... weird. There's also a tune before he swipes the pass over his belt, but it's just like someone mucking around with a synthesizer, and not as elaborate as some of the others. Eve's face also takes a place on his chest, sort of like the Vega Forms.