Gleipnir

Shuuichi Kagaya seems like a typical high schooler—until the moments when he inexplicably transforms into a monster. With no clear idea how he gained these powers, he keeps them hidden, hoping no one ever finds out. One night, he spots a building on fire and rescues a girl trapped inside, but in the chaos he leaves behind his phone.

The girl, Claire Aoki, soon tracks him down and corners him about what she saw. When Shuuichi insists she’s mistaken, Claire forces the issue by pushing him from the school roof, leaving him no choice but to transform to survive. She captures proof and uses it to pressure him for information about other monsters—answers he can barely provide. Claire reveals her own motive: she’s searching for her sister, who has also become a monster, and she needs Shuuichi’s help to find her—while others pursue the same mysteries for their own reasons.