Danshoku Dino
Takanashi was first trained in professional wrestling by Último Dragón at his Último Dragón Gym. After failing to graduate from his class, Takanashi moved to the training dojo of the Dramatic Dream Team (DDT) promotion. From August 19 to September 6, 2003, Takanashi wrestled several exhibition matches for DDT, before making his official debut for the promotion on September 14, where he, now working under the shortened ring name Masa Takanashi (spelled in western naming order [given name first]), was defeated by Super Uchu Power. For the rest of the year, Takanashi wrestled mostly opening matches, picking up his first win on December 29, when he pinned Daichi Kakimoto in a six-man tag team match. In early 2004, Takanashi began regularly teaming with Danshoku Dino. On May 29, Takanashi defeated Shoichi Ichimiya in the first round for the inaugural King of DDT tournament. The following day, he was eliminated from the tournament in the semifinals by Danshoku Dino. From April to May 2005, Takanashi represented DDT in Kaientai Dojo's K-Metal League, where he failed to make it to the finals. Upon his return to DDT, Takanashi began wrestling as a representative of DDT's Cruiser's Game project. In January 2006, Takanashi was, in storyline, brought under the spell of Poison Sawada Julie and turned into a human snake. Takanashi would wrestle as a member of Julie's Snake Corps, before managing to break away from the group in May, along with Seiya Morohashi. On June 25, Takanashi won his first championship, when he, working as Masahiro Mekanashi, a character inspired by the Mecha Mummy, defeated Mecha Stanley for the Ironman Heavymetalweight Championship. Takanashi then entered a battle royal, where he lost the title to Natsuki☆Head, before regaining it from Mikami and then losing it to Mecha Mummy. Also in 2006, Takanashi made his debut for El Dorado Wrestling, where he worked alongside his Último Dragón Gym training partners as King Pocota. The character then moved to DDT, where he was renamed Poco Takanashi and won the Ironman Heavymetalweight Championship two more times, each time holding the title less than a day. On November 23, Takanashi won his first major title, when he and Seiya Morohashi defeated Francesco Togo and Mori Bernard for the KO-D Tag Team Championship. After a five-month reign, Takanashi and Morohashi lost the title to Michael Nakazawa and Tomomitsu Matsunaga on April 1, 2007. After returning to performing as Masa Takanashi, he defeated Danshoku Dino and Kudo in a three-way match on February 20, 2008, to win the DDT Extreme Championship. He would go on to lose the title to Francoise Takagi on July 6. During the summer of 2008, Takanashi formed the "Belt Hunter×Hunter" stable with Danshoku Dino, Hikaru Sato, Keisuke Ishii and Tigers Mask. The stable's storyline rivalry with the Italian Four Horsemen stable built to an eight-man tag team match on December 28, 2008, where the loser of the fall would be banished from DDT. The match ended with Horsemen member Antonio Honda pinning Takanashi for the win; as a result, Takanashi was, in storyline, forced to leave DDT.