Morimoto was born in Kawasaki on May 7, 1988. He joined J1 League club Tokyo Verdy from their youth team in 2004. On March 13, Morimoto made his J1 League debut for Tokyo Verdy against Júbilo Iwata at the age of 15 years, 10 months and 6 days, a league record for youngest player to debut. He scored his first goal against JEF United Ichihara on May 5, two days before his 16th birthday, another league record for youngest goal scorer. He was selected "J.League Rookie of the Year Award" in the 2004 season. Verdy won the champions in the 2004 Emperor's Cup. However Verdy was relegated to J2 League end the of 2005 season. In summer 2006, he moved to Italian Serie A club Catania. He played for the club in 5 seasons. In summer 2011, he moved to Novara. In summer 2012, he re-joined Catania. In January 2013, he moved to UAE Pro League club Al-Nasr. In summer 2013, he returned to Japan and joined J2 club JEF United Chiba. In 2016, he moved to J1 club Kawasaki Frontale. Kawasaki won the J1 champions in 2017. In 2018, he moved to J2 club Avispa Fukuoka. In October 2020, he moved to Football League Greece club AEP Kozani. In February 2021, he moved to Paraguayan Primera División club Sportivo Luqueño