Keisuke Sannan, sometimes known as Keisuke Yamanami in other series, is the bespectacled captain of the Shinsengumi. Both a scholar and a ruthless tactician, he is kind and caring, albeit a bit reserved.

Spoiler

After an injury which resulted in him being unable to use his sword arm, he has become cold and suspicious of others. Hope of regaining the use of his arm has led him to drink ochimizu; he is the first of the characters introduced to do so.