Re:ZERO: -Starting Life in Another World-, Vol. 1 (manga)

"Subaru was just a guy in a tracksuit until he was summoned to another world. When his life is saved soon after by a beautiful girl with silver hair and her fairy-cat sidekick (yeah, it's that kind of place), he's determined to repay the favor. But not only does he know nothing about the dangerous realm he's been transported to, he has also acquired the most inconvenient special ability of all time. His efforts to save the girl who saved him might get him killed, but for Subaru Natsuki, death is only the beginning"--Back cover.