Sekai wa Summer Party (世界は サマー・パーティ; The World Is a Summer Party) is the 3rd major single by Mano Erina. The single was released on July 29, 2009 in 3 Limited Editions, and Regular Editions with both the Limited A and B coming with bonus DVDs. All three limited editions came with a serial number card used to enter a lottery where tickets could be won to an event. The single reached #10 on the Oricon charts and charted for five weeks, selling a total of 18,647 copies. S/mileage is featured as back-up dancers in the PV and accompany Mano in live performances of the song.