A monk who served as an official under Kennyo at Ishiyama Hongan Temple, he along with Suzuki Shigehide commanded the Hongan Temple army against Oda Nobunaga. For this reason they were called the "Left and Right Generals of Osaka".

When Hongan Temple surrendered to the Oda army in 1580 by order of the Emperor, Rairen's signature was among those on the official letter. Afterwards, he left with Kennyo to persuade the Ikkou-ikki of various parts of the country to rise up against Nobunaga.

After Takeda Shingen's death, when both Toyotomi Hideyoshi and Tokugawa Ieyasu requested help from the Ikki forces, Rairen opposed and remained neutral throughout. In 1589, Hideyoshi bestowed land on him and made him a magistrate.

In Mirage of Blaze: he continues to clash against Nobunaga and eventually performs kanshou on a man of some means named Watanabe, who appears to be a man of amiable disposition and wears silver-rimmed glasses.