This year, Haruhi is now in her second year in high school, and is still searching for mysteries and strange events; as usual, she doesn't find a single one. Even so, she does meet a strange new exchange student from another country, and reluctantly offers him a place at her house after his admission that he doesn't have anywhere to stay.

However, Haruhi is unaware that this new student is one of the Dimensional Sliders that came into existence after she wished for them years ago, along with aliens, time travelers and espers.

The new student's name is Alan, and his confusion at being dropped off all too suddenly in Haruhi's universe is later clarified by three other Dimensional Sliders. These Sliders that Alan interacts with all come from a variety of places: Kanata Izumi (Lucky Star), Saya Minatsuki (Black Cat), and Fuko Ibuki (Clannad).

[From Official Site]