BBL is "Bad Boy's Love," also considered the "true" route. You'll unlock it after completing the routes for Ryouta, Sakuya, Yuuya, Nanaki, and Nageki. If you're loading pre-existing saves to start all the routes, you'll have to create a new one for this route.

There's also an epilogue if you've completed every single other route, and I'd advise all the routes first anyways to learn about the characters as the route wouldn't be the same experience without doing everything else prior.

Here is Holiday Star, set in an AU: https://store.steampowered.com/app/377080/Hatoful_Boyfriend_Holiday_Star/
They're also working on a third game, HB: Mirror, based on Holiday Star but yet another AU
And then there are some shorter special routes here: http://clione.halfmoon.jp/hatoweb/english.html