query: Who is the most successful team in the World Sudoku Championship? 
answer: Japan is the most successful team, having won the World Sudoku Championship title in 2007, 2012, 2014, 2015 and 2018; Czech Republic (2008, 2016), Germany (2010 and 2011) and China (2013, 2017) have won twice; Slovakia (2009) also won a title.