Girls' Generation announced the single "Catch Me If You Can", their first release as an eight-member group, in March 2015. It was recorded in both Korean and Japanese; the Korean version was released worldwide on April 10, while the Japanese version was released on April 22, 2015. It peaked at number nineteen on the Gaon Digital Chart and number eight on the Oricon Singles Chart.  Girls' Generation revealed the cover artwork of their fifth Korean studio album Lion Heart on August 12, 2015. It was subsequently released by S.M. Entertainment on August 19, 2015. The album peaked atop the Gaon Album Chart, and at number eleven on the Oricon Albums Chart. Lion Heart was the thirteenth best-selling album of 2015 in South Korea, with sales figures standing at 145,044 units.  Lion Heart produced three singles--the first being "Party", which was released in July 2015. It peaked atop the Gaon Digital Chart, at number ten on the Japan Hot 100, and number four on Billboard's World Digital Songs. Following the release of "Party", Girls' Generation appeared on the Billboard Social 50 at number forty-four on August 1, 2015. The following week, the group's position on the chart rose to number twenty-two. The follow-up singles "Lion Heart" and "You Think" were made available in conjunction with the release of the album. They charted at numbers four and thirty on the Gaon Digital Chart, respectively.  To promote the album, the group starred in a South Korean reality television program titled Channel Girls' Generation. They further embarked on their fourth concert tour, Girls' Generation's Phantasia, which started on November 21, 2015 in Seoul. With this achievement, Girls' Generation became the first South Korean girl group to hold a fourth concert tour. The group also concurrently embarked on their 4th Japan Tour, which commenced on December 12, 2015 at Nagoya. By year-end, the Gaon Music Chart announced that Girls' Generation was the most successful girl group of South Korea for 2015. With the release of their Lion Heart album along with two other albums, by subgroup TTS and member Taeyeon, they together sold over 398,000 physical copies.  The group was on a hiatus for the most part of 2016. However, to commemorate the group's ninth debut anniversary, in August 2016, a single titled "Sailing (0805)" was released. The lyrics were written by member Sooyoung, highlighting the relationship between the group and their fans.

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