The line of overlapping sentences is the main line of LB, telling the story of the little organization Busters, and also telling you the secret of the world.

LB was released in 2007, which can be regarded as the original work, while LB EX was released in 2008. The main difference is that Ma Zhizhun started writing again in EX. In addition to retouching the original story, it was banned on 18 (you are not mistaken, LBEX is all-age, and LBEX is banned on 18), and three female corner lines were added.

As for the game, I suggest you go to KeyFansClub forum to find it. I believe the content inside can deepen your understanding of the game.