Gleipnir 2

Shuichi's normal life ended when he first transformed into a monster, but meeting the dangerous Claire has sent them both down an even darker path. Now that Claire has discovered she can control his freakish costume-like form by climbing inside him, she's certain that her killer instinct and Shuichi's brute strength will make them an unstoppable team—but neither of them are ready for the horrors they're about to face.

Volume 2 of the Gleipnir manga series by Sun Takeda.