Kamen Rider 1 Through RX: Big Gathering is a TV special which covers all the Kamen Riders, from Kamen Rider 1 until ZX and introduces Kamen Rider Black RX.
Kamen Rider 1 Through RX: Big Gathering
Though a TV special airing in the gap between the final episode of Black and the first episode of Black RX, it was variously treated as the end of Black and the start of RX. A teaser trailer for Kamen Rider Black RX was aired following the broadcast of the final three episodes of Black, advertising it as starting on October 16th, refering to this special and not the first episode (which would air on October 23rd).
Kamen Rider 1 Through RX: Big Gathering
On the other hand, the ‘finale’ of Black was followed by a standard next time trailer, for this special and it would be counted as ‘episode 52’ of Black on the DVD release. A clipshow, it’s mostly composed of narrated footage of the first eleven Kamen Riders in their series and the then-upcoming premiere of Kamen Rider Black RX.