Return of Watch Mask is before Season 1. As the Main Character is Jino along with Luna. This is the first appearance of Kai, Schmidt and the others.
Plot (Spoilers!!)
A mysterious letter was delivered to ‘Gino’, the Heroes Cup champion! It was an invitation to the ‘Ultimate Watch Car Battle League (UWB)’, which is known for being violent. Finally, on the day of the UWB game, I was attacked by unidentified assailants on my way home after watching the game. ‘Gino’s’ watch car, Bluewill, is kidnapped, but after many twists and turns, Bluewill is recovered. ‘Gino’, who found out the identity of the assailants, became ‘Watch Mask’ and hid his identity to prevent their plot. He participates in UWB with Blue Will, who has transformed into Blue Thunder... Will Watch Mask be able to emerge as a new hero in UWB?