Tritops.

Tritops (트리탑스) is a South Korean boy group managed by Van Leader Entertainment. Tritops began activities on October 19th, 2007 with three The known members are Hyungmoon, Ilgoon, Yoojun. Additional background says that After the company changed to DoReMi Media, Ilgoon left to pursue a solo career in 2009. The profile also notes that The group promoted shortly as a duo, but were joined by new member Woogon in 2012 and moved to Simtong Entertainment. Another profile detail is that in 2013, Ilgoon returned to the group. Additional background says that Following his return in 2014, the group moved to new company called Van Leader Entertainment. The profile also notes that they officially debuted in Japan on October 27th, 2014 and have been mainly active there since then.