Asai Nagamasa

Sengoku daimyo in Omi - this state included the north shore of Lake Biwa which was crucial to the defence of Kyoto. The Asai base was at Odanijima. The family name is sometimes (mistakenly) pronounced 'Asai'.
In 1563, Nagamasa married Nobunaga's sister, O-ichi, and thereafter began to expand his power. In 1568, he joined forces with the Oda to destroy the Rokkaku, gaining control of some half of Omi. In 1570, Nobunaga broke his word invaded Echizen, at which Nagamasa, heedless of his father, Hisamasa's, advice, betrayed Nobunaga and allied with the main family of Echizen, the Asakura, whom Nobunaga was attacking. Nagamasa attacked Nobunaga, but the Asai-Asakura forces were wiped out at the Battle of Anegawa.
After this defeat, Nagamasa tried to restore his fortunes by allying with Takeda Shingen, the temple of the Hongan-ji, and the monasteries of Mr Hiei, but in the eighth lunar month of 1573 his castle of Odani was violently attacked, and when it fell, Nagamasa committed suicide.