"Because of You" (Hangul: 너 때문에; RR: Neo Ttaemune) is the second single released by South Korean girl group, After School. The group also released an official remix version of "Because of You" on 21 January 2010. The title track was written, composed, and arranged by Brave Brothers, and it was the first release without member So-young and with new members Raina and Nana.

Before After School made their comeback with "Because of You", Pledis announced the graduation of Soyoung and that two new members are to be added: Raina and Nana. Pledis then released teaser pictures showcasing a more mature concept with the members dressed in black and white suits, a change to their sexy concept that they debuted with. On November 23, a music video teaser was uploaded and gained over 200,000 views in 24 hours. A remixed version of the song was released in January 2010.

The group officially made their comeback on SBS's Inkigayo performing "When I Fall" and "Because of You". The group then performed on Inkigayo, KBS's Music Bank and MBC's Music Core on a weekly basis to promote the song. After School did not perform on Mnet's M! Countdown due to conflicts between Pledis and the broadcasting company. Pledis stated that the conflicts were "concerning the fairness of the MAMA awards."

Shortly after the song was released, the song topped various online music charts in South Korea and was an instant hit. The song achieved a daily and weekly "all-kill" by topping all daily and weekly charts on online music stores. "Because of You" then debuted at #1 on the Gaon Digital Chart for the month of December, which was a rarity for rookie groups from small agencies. It also went on to win a triple crown on SBS Inkigayo. The song has since been downloaded over 4,000,000 times, becoming After School's best selling song to date.

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