A young and ambitious ruler of the Date clan who seeks control of the land, and is known as the "One-Eyed Dragon" because of his missing right eye. He becomes friends with Magoichi Saika in his story mode. With the typical arrogance of a teenager, he calls everyone around him "Idiots," "Imbeciles" and "losers". His ambition is to open Japan to foreign trade and to explore other lands. He is seen as an immature annoyance by pretty much everyone, partly due to his habit of constantly charging in unexpected and uninvited into battles between other clans and attacking both sides. In the second installment, his teenage arrogance is generally directed at Kanetsugu Naoe, who's values of love and righteousness contradict his great ambitions of personal gain, resulting in a bitter rivalry between the two. In the first game, he is shown to be around the physical age of eleven or twelve and is teased by every character he meets for his tender age. In the second installment, however, he is fifteen or sixteen and has garnered more respect and clout as a formidable warlord. He also seems to have, more or less, grown out of his habit of interfering with battles and ambushing both armies, and his blind lust for power has shifted to a desire to change and improve Japan. He is set to appear in the third installment, with minor costume changes with the appearance of a young adult.
Masamune has a high rate of attack and moderate range. Initially, he wields a pair of bokken (wooden swords) called "Botenmaru" (in reference of his childhood nickname). In Samurai Warriors 2 however, his weapons are changed to a western-style saber and a pair of pistols, collectively known as "Manhunter." He has a Musou attack which involves him shooting wildly into the surrounding crowds with his pistols.