Ikkyuu

About
Ikkyuu serves the Ashikaga House as the chief adviser of Ashikaga Choushin. He is a strange but nonetheless effective strategist who loyally serves Choushin. He possesses a Youkai Phone, which he uses to call to "mother". It is hinted several times that he is in fact a youkai, though 3G strongly denies this, even though he dialed to Ikkyuu by accident on his Youkai Phone.

Sengoku Rance
As the chief advisor, Ikkyuu is the one responsible behind the most (if not all) plans to defeat Oda, though none seems to succeed.

One of his most noted plans is when he suggested Ashikaga to send a messenger to Oda, in order to obtain the reparation fee for the disgrace that Ashikaga House received during the union. The plan seems to succeed until Rance decided to just kill the messenger instead of "paying for peace". This is the trigger for Ashikaga to declare war against Oda.

Ikkyuu won't be available in the prison even after Oda conquered Ashikaga House entirely. It's implied that he escapes. He often appears as another house's officer after the fall of Ashikaga.

Despite that, it's still possible to capture him in battle.

In a event it is revealed he ordered tarou's death.

Trivia

 * Ikkyuu's overall appearance is a reference to old Japanese anime called Ikkyu-san and Vinegar Doppio from JoJo's Bizarre Adventure. See also Ikkyū for historical reference. The Japanese wikipedia entry noted that recent research suggests Ikkyuu might be the son of Emperor Go-Komatsu, the 100th emperor of Japan.
 * He has a "witty comeback" ability, which allows him to turn the tide of battle into a certain win. In Sengoku Rance, the player can use this ability, though the usage of this ability is limited.