Most of the versions of the game are all-ages, but "Little Busters! Ecstasy" is for 18 and up, so make sure you don't mistake which version you're buying.

The new material from Ecstasy, other than the ero materials, is included in the Converted Edition.

Little Busters!	PC	2007	All Ages	In this version only, there are only 6 playable heroines.
Little Busters! Ecstasy	PC	2008	18 and up	From this version onward, there are 9 playable heroines
Little Busters! Converted Edition	PS2→PSP→PSVita	2009~	13 and up	Fully voiced
Little Busters! Perfect Edition	PC	2012	All Ages	Material from CE reverse-ported to PC

Story

The protagonist, Naoe Riki, goes to a dormitory high school with his childhood friend Natsume Kyousuke, Kyousuke's little sister Natsume Rin, and their other childhood friends Inohara Masato and Miyazawa Kengo.

In the past, the five of them formed a team called the "Little Busters" and used to play at vanquishing evil in their neighborhood. To Riki, who at the time had lost his parents and was very depressed, the other four are precious friends who brought him into and taught him about the world around him. Even the way that his friends sometimes dragged him into ridiculous things and acted without thinking felt fun to Riki, and he thought that he wanted his time with them to last forever.

One day, Kyousuke--who was in his final year of high school--came home from looking for work. Riki proposes to the other four members of the Little Busters that they do "something" like what they used to. And hearing that, their leader Kyousuke picks up a nearby ball from the ground and proclaims:

"Let's make a baseball team. Our team name will be... Little Busters!"