Aoiyama Kōsuke (Japanese: 碧山 亘右, born 19 June 1986 as Daniel Ivanov (Bulgarian: Даниел Иванов)) is a Bulgarian professional sumo wrestler or rikishi from Elhovo. He made his professional debut in 2009, reaching the top division two years later, debuting in the November 2011 tournament. He has won four Fighting Spirit awards, one Technique award and one kinboshi for defeating a yokozuna. He has twice been runner-up in a tournament. His highest rank has been sekiwake. He is one of the heaviest competitors in sumo, weighing around 200 kg for most tournaments.