What is "soulja"

is a Japanese hip-hop musician and songwriter. He is best known for his collaborations with singer Thelma Aoyama, " Koko ni Iru yo" and " Soba ni Iru ne" - the latter of which was the former Guinness World Records holder for the best selling digital single of all-time in Japan (until it was superseded by Greeeen's " Kiseki").