Lee Jae Jun, also known as Marcus and formerly known as Maru, is a South Korean singer, dancer, former member of C-CLOWN, TREI and TAN and current member of the duo JT & MARCUS and IN A MINUTE. He graduated from Heungdeok High School and is enrolled at Cheongju University.

He made his debut in July 2012 (at the age of 15) as C-CLOWN's lead rapper, lead dancer, vocalist and maknae with their first mini-album, "Not Alone" (using the stage name Maru). The group was managed by Imagine Asia (formerly known as Yedang Entertainment). In October 2015, the agency announced C-CLOWN was disbanding, so he decided to leave the agency. He began using his birth name and, in 2017, switched agencies.