Kōsa , also known as Hongan - ji Kennyo ( 本願寺 顕如 ) , was the 11th head of the Hongan - ji in Kyoto , and Chief Abbot of Ishiyama Hongan - ji , cathedral fortress of the Ikkō - ikki ( Buddhist warrior monks and peasants who opposed samurai rule ) , during its siege at the end of the Sengoku Period . He engineered many alliances , and organized the defenses of the cathedral to the point that most at the time considered Ishiyama Hongan - ji to be unbreachable . In 1570 , Takeda Shingen , a relative of Kōsa through marriage , faced not one but three major rivals : Oda Nobunaga , Tokugawa Ieyasu , and Uesugi Kenshin . He asked the Abbot for aid , and Kōsa persuaded the Ikkō sectarians ( also called Monto ) in Kaga Province to rise up against Uesugi Kenshin . Several years later , after the death of Takeda Shingen , Kōsa secured the aid of the Mōri clan in fighting Oda Nobunaga and defending the Hongan - ji ' s supply lines from blockade . Oda Nobunaga ' s Siege of Ishiyama Hongan - ji began in 1570 , and would be the longest siege in Japanese history . In accordance with Kōsa ' s strategic organization of the defenses and alliances , the fortress was all but impervious to attack , and the Mōri clan fleet defended the supply lines for some time . Kōsa ( and the Mōri ) requested aid from both Takeda Katsuyori ( son of Shingen ) and Uesugi Kenshin , as well as the Ikkō armies of other provinces , to attack Nobunaga , relieving the siege . But neither Takeda nor Uesugi answered his call . When Nobunaga attacked the fortress with 3 , 000 troops , the monks answered with 15 , 000 ; Nobunaga then turned to attacking Kōsa ' s allies , the Asakura , Uesugi , and Azai clans as well as other outposts of Ikkō - ikki monks . The Abbot wrote a desperate letter to Ikko followers in Musashi and Sagami Provinces , asking them to stand fast , and to send supplies and reinforcements . The fortress ' supplies were nearly exhausted , and their outposts were nearly all destroyed by 1580 . Nobunaga ordered the Abbot to evacuate the fortress , and to leave Osaka . Kōsa deliberated with his allies , particularly the Mōri , and then left for Kii Province , hoping to raise reinforcements . He left his son in charge of the fortress , who surrendered after an Imperial Messenger arrived with an official request from the Emperor that he do so . The fortress mysteriously burned down after the monks left it . Despite this incredible defeat , Kōsa remained devoted to the Ikko sect , and to the idea of regaining a central cathedral fortress for the sect . He began to enlist the help of Ikko sectarians to aid Toyotomi Hideyoshi , in order to gain Hideyoshi ' s favor . In 1583 , Kōsa sent Ikko warriors to harass Hideyoshi ' s enemy Shibata Katsuie , and in 1587 he sent messengers to Kyushu , asking Ikko leaders there to act as guides for Hideyoshi ' s army in Satsuma Province . In 1589 , Hideyoshi granted Kōsa his wish for a new Hongan - ji . The site was the shrine to the patriarch Shinran , in Kyoto ; it was moved in 1591 , and is now known as the Nishi Hongan - ji . In popular culture . In fiction , Kōsa usually appears with the name Honganji Kennyo . Kennyo appears as a non - playable character in Koei ' s video games " Samurai Warriors " , " Kessen III " and " Mōri Motonari : Chikai no Sanya " , > and in Capcom ' s " Sengoku Basara 2 " .