"Sekaiichi HAPPY na Onna no Ko" is the twenty-second single (seventeenth major label single) released by °C-ute. The single was released in limited A, B, and regular editions, both limited editions coming with bonus DVDs. The limited editions and the first press of the regular edition came with a serial number card which, when entered in a lottery, could win a ticket to one of the single's launch events. The single reached #6 on the Oricon charts and charted for three weeks, selling 19,830 copies making it the lowest selling single from them. The Single V reached #9 on the Oricon charts and charted for one week, selling 1,610 copies. The Event V was sold only during launch events, and therefore did not chart.
