セイバー＋ゼンカイジャー スーパーヒーロー戦記

Touma, Yuri and Mei somehow ended up in the World of Zenkaiger while four Zenkaigers, except Juran, ended up in the World of Saber. The reason for their swap is due to a man who wishes to rid the world of heroes. How does a teenage boy manga artist tie into this? And why are they sent into different stories filled with previous Kamen Riders and Super Sentai Teams?