Here's a breakdown:
* Junjo Romantica Pure Romance season 1 covers the first 13 episodes of the anime, adapting the first volume of the manga. It focuses on the relationship between Miyagi and Usami.
* Junjo Romantica Pure Romance season 2 covers episodes 14 to 26, adapting the second volume of the manga. It continues to focus on Miyagi and Usami's relationship, while also introducing the other main couples from the manga: Takatsuki and Hiroki, and Shinobu and Akihiko.
So, while both seasons are part of the Junjo Romantica Pure Romance anime series, they cover different parts of the manga and have different storylines.