1545 - 1573
Appearances: Sengoku Musou (1NPC,2), Sengoku BASARA (2NPC)
Note: 浅井 can be also read あさい Asai.
He was first known as 浅井賢政 Azai Katamasa. Daimyo of 近江 Oumi and owner of the 小谷 Odani Castle. Son of 浅井久政 Azai Hisamasa. He was proposed by his father to marry the daughter of a 六角 Rokkaku retainer, however he rejected that. As a result, the Azai and Rokkaku broke into war. Eventually, the Azai were able to weaken the Rokkaku. Nagamasa would then assume control of the Azai, after his retainers forced Hisamasa to step down. He would then advance to Mino and clashed with the 斉藤 Saitou, while at the same time the Oda were also attacking the same region. Azai and Oda would form an alliance, with a note that if the Oda was to engage the 朝倉 Asakura, Azai's close ally, they should consult with the Azai first. From this alliance, Nagamasa married Nobunaga's sister, O-Ichi.
However in 1570, Nobunaga attacked the Asakura. It is said that Nobunaga didn't even consult with the Azai, and thus Nagamasa decided to break the alliance despite his marriage with Ichi. The Azai-Asakura alliance would clash with the Oda several times, including in the battles of Anegawa and Usayama. The climax of this conflict was in 1573, when Nobunaga laid a siege on Odani. The Asakura were quickly decimated by Nobunaga in Echizen, so Azai was now isolated. Nagamasa had no more choices but to return Ichi and their three daughters to Nobunaga, while he and his son would commit seppuku inside the castle afterwards.