Blade of the Immortal

Ever since the Dewanosuke incident, Burando kept making blunders. He is finally thrown in solitary confinement by Habaki, and goes insane. But as a result of his madness, Burando grasps something important about the immortality experiments: That humans are essentially otters. Meanwhile, Rin and Doua resolve to infiltrate Edo Castle to rescue the surrounded Manji and Isaku.