Kamen Rider Agito: A New Transformation

Originally aired between episodes 35 and 36, the Special features all three Riders plus the first appearances of G3 Mild & Agito Shining Form. Shouichi encounters his old friend and teacher and fights an Unknown at night and reaches Burning Form, but goes out of control. Then, the teacher helps him control it. All three Riders fight against the Beetle Lord. The story is ended with a mysterious girl stalking G4 project and to be continued in the movie.
(Source: Kamen Rider Wiki)