Ep 5. The Crimson Black Assassin

In Black Bullet season 1 episode 5, titled "The Crimson Black Assassin," Rentaro and Enju are tasked with fighting a powerful Gastrea that has taken over a hospital. However, they soon realize that they are not the only ones fighting the Gastrea- there is also a mysterious girl dressed all in black, who seems to be attacking both the Gastrea and anyone else who gets in her way.

As Rentaro and Enju struggle to figure out who this girl is and what her motives are, they find themselves up against a powerful and dangerous opponent. The girl, who calls herself "Kagetane Hiruko," is an extremely skilled fighter and seems to have a personal grudge against Rentaro.

Meanwhile, the fight against the Gastrea rages on, with Rentaro and Enju struggling to hold their own against the powerful beast. With the help of some unexpected allies, they manage to push back the Gastrea and save the hospital- but the mystery of Kagetane Hiruko remains unsolved.

As the episode comes to a close, Rentaro grapples with the realization that his fight against the Gastrea may be far from over. Kagetane Hiruko may be just the first of many powerful enemies he will face in his efforts to protect the city from the deadly creatures.

Overall, Black Bullet season 1 episode 5 is a tense and action-packed installment of the popular anime series, with plenty of twists and surprises to keep fans on their toes. Whether audiences are longtime fans of the show or new to the series, this episode is sure to be a standout, with strong performances, thrilling fight sequences, and plenty of suspense and mystery.