Ai Otsuka (Da Zhong  Ai , Otsuka Ai, born September 9, 1982) is a Japanese singer-songwriter from Suminoe-ku, Osaka, Japan. She is a popular artist on the Avex Trax label and is best known for her 2003 hit "Sakuranbo," which stayed in the Top 200 Oricon Weekly Singles Chart for 103 weeks. A piano player since age four, Otsuka composes and co-produces her own songs, as well as writes her own lyrics. Her music ranges from upbeat pop/rock music to ballads.

In November 2004, the follow-up to Love Punch, Love Jam, was released, which met even greater popular success. Along with three single released before her second studio album was released. First, "Happy Days" sold 163,433 units and reached third on the Oricon weekly chart. Love Jam Tour 2005, her first tour, began on April 24, 2005. It was completed in June 2005 and a live DVD with footage was released on July 27, 2005. Love Cook, her third album was released on December 14, 2005.  "Kingyo Hanabi" was the second single to be released after her first album. "Kingyo Hanabi" also landed in third on the Oricon weekly chart but was able to sell 148,121 units, about 20,000 copies less than her "Happy Days" single. Two months later, Otsuka released another single, "Daisuki da Yo". Like the previous two singles, it reached number 3 on the Oricon weekly chart and sold 156,844 units.  Otsuka released her second studio album a month later in November 2004. Love Jam debuted at the number one position and sold 224,381 units in its first week. In total, 656,700 units were sold. Love Jam became her first album to top the chart, but at the same time it was her lowest selling studio album. Love Jam was released in two different versions including a CD and a CD+DVD version. Following the release of Love Jam, Ai Otsuka released the recut single "Kuroge Wagyu Joshio Tan Yaki 680 Yen" in February 2005. It was a different version of the "Kuroge Wagyu Joshio Tan Yaki 735 Yen" track on Love Jam. "Kuroge Wagyu Joshio Tan Yaki 680 Yen" is arranged differently in terms of music and vocals. This single sold 149,134 units and debuted third on the Oricon weekly chart and was the sixty-eighth single of 2005. It was the first ending theme song for the anime Black Jack. Answer this question using a quote from the following article:

What was a popular single off the album?
Happy Days