LIGHTSUM (라잇썸) is a six-member South Korean girl group formed by Cube Entertainment. The group debuted June 10, 2021 with Vanilla, presenting a bright performance-based sound and an optimistic identity built on the idea of gathering different lights. The current members are SANGAH, CHOWON, NAYOUNG, HINA, JUHYEON and YUJEONG.

After beginning with eight members, the group moved to a six-member formation in October 2022 following the departures of HUIYEON and JIAN. Releases such as VIVACE, ALIVE, Honey or Spice and POSE! chart the transition from cheerful debut concepts toward more confident pop arrangements.

In 2026 LIGHTSUM launched an ambitious Japan major-debut project. The ABEMA documentary Re:Idol, debuting August 9, followed the group’s attempt to reimagine aspects of their sound and presentation for a Japanese idol audience. Warner Music Japan released the five-track Re:idol on September 23, including new songs どうして, Fallin’ World, Stop and Go and 夜を歩く君へ, alongside POSE! (Kawaii ver.).

The project represented a significant stylistic pivot without changing the core six-member identity. HINA’s Japanese background and the group’s Korean idol-training foundation make this cross-market chapter especially distinctive. Their fandom is known as SUMIT.