Len is a young man from Ventara, the world behind the mirrors. Along with eleven others, he was chosen to become a Kamen Rider, a warrior to defend his planet from the evil alien Xaviax who planned to take over Ventara. With the power of his Advent Deck, Len transforms into Wing Knight, with the aid of Black Wing, the spirit of the bat. Len, being the only survivor takes it upon himself to carry out his mission and stop Xaviax from taking over Earth the way he took over Ventara. Due to the many hardships he's had to endure (losing his entire planet, his fellow Riders, and having his best friend turn on him) Len has become kind of a loner, withdrawing his emotions into a shell, no longer putting faith and trust in people. After Kit Taylor, a teenager from Earth, contracts with the Dragon, Len realizes he must train Kit in the fight against Xaviax, and try to keep Kit from falling into Xaviax's trap the way the original Riders did.
As Len spends more time with Kit, and with Maya, a young woman who is a reporter for an online blog and who has decided to help Kit and Len with their mission, he begins to let the walls he placed around his heart fall down, and we soon see that he is a very gentle and caring person. However, the longer the mission lasts and the more times he fails, he feels like a weakling and struggles with his feelings. What will Len do next? Only time will tell...