He is introduced as the cocky and opportunistic Daimyo of Oumi, who proposes an alliance with Nobuna on the condition that she marries him, which she nearly accepted and eventually turns down the offer.

Spoiler

It is later 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.