Tanahashi also defeated Tiger Mask on May 13 in the first ever main event of the new Wrestle Land brand (a promotional experiment by New Japan with "sports entertainment"), debuting a modified side buster finish. On June 7, Tanahashi vacated the U-30 Openweight Championship in order to fully focus on his upcoming match against Brock Lesnar for the IWGP Heavyweight Championship. When Lesnar failed to show up for the match, he was stripped of the title and Tanahashi was placed in a tournament for the vacant title. On July 17, Tanahashi won his first IWGP Heavyweight Championship when he defeated Giant Bernard in the finals of the tournament for the vacant title. He showed the title belt on his second appearance on Sasuke during the 17th competition, where he was again eliminated in the first round. After holding the title belt for almost 9 months (270 days) and defending the title against the likes of Taiyō Kea, Shinsuke Nakamura and others, Tanahashi lost the title to Yuji Nagata, who had won the 2007 New Japan Cup to become the No. 1 contender. Tanahashi managed to come back from this by winning the 2007 G1 Climax, where he defeated Nagata in the finals and successfully challenged his rival to a rematch on October 8, 2007, where he pinned Nagata to regain the title. On January 4, 2008 at New Japan's annual Tokyo Dome show titled Wrestle Kingdom II in Tokyo Dome, Tanahashi was defeated by Shinsuke Nakamura for the IWGP Heavyweight title in the night's main event. In February's New Japan "Ism" tour, Tanahashi successfully defeated A.J. Styles in a highly anticipated rematch of their 2006 bout in Total Nonstop Action Wrestling (TNA). Following this, Tanahashi was entered into the coveted New Japan Cup tournament in which the winner would face off against the then-IWGP Heavyweight Champion Shinsuke Nakamura as the number one contender. With a win over Giant Bernard, Tanahashi became the first two-time winner of the New Japan Cup. Mid-February, he was embroiled in a contract dispute with New Japan. While negotiations were ongoing, Tanahashi took advantage of his free agent status to compete in All Japan Pro Wrestling's Champion Carnival. He came in as a villain and was given the "Block from Hell" as he had to face nearly all of All Japan's top talent including Taiyō Kea, Satoshi Kojima, Toshiaki Kawada and his mentor Keiji Mutoh.