Manga Dial Again

Following a near-death experience, an otherwise ordinary young man named Noah finds out that he has become immortal. Deciding to make good use of his abilities, he becomes a bodyguard, but an unexpected side effect of his powers forces him to quit the job.

It's then that he meets a shady-looking man named Allen Walker, who offers to take care of that particular side effect in return for his resuming bodyguard work...