He was introduced in episode 3 as the cocky and opportunistic Daimyo of Oumi, who, in the said episode proposes an alliance with Nobuna on the condition that she marries him, which she nearly accepted and eventually turns down the offer. In episode 7, he renewed his proposal to Nobuna because he cannot return home for fear of being embarrassed, only this time there are no strings attached for forming an alliance and he gets to have Nobuna's sister, Oichi - who unknown to him is actually Nobusumi dressed up as a girl to be his bride.
In episode 10, however, it is revealed that Nagamasa is actually a woman hiding her real gender because of her strict father who wants a man to lead the Asai clan. If Nagamasa had chosen to be herself, to stay a woman she would have been sent to Rokkaku as a hostage. So she decided to abandon all female habits to become a man instead.
