Yokozuna promotion-chasing ozeki Kirishima joined six other wrestlers at the top of the Nagoya Grand Sumo Tournament leaderboard on Saturday after rank-and-filer Shishi suffered his first defeat after seven days of action.Kirishima (6-1) had to fight his way back from a patchy start against last year's Nagoya meet winner, sekiwake Kotoshoho (3-4), with the ozeki finding himself on the back foot before coming to a standstill in the middle of the raised ring at Nagoya's IG Arena.A deep left-handed belt hold proved vital for Kirishima, who went 12-3 in May and could rise to yokozuna by posting a championship-caliber result this month, as he outlasted his opponent to win by a well-executed overarm throw.Yokozuna Hoshoryu (5-2) got back to winning ways against Hiradoumi (1-6), albeit backing o…