Also, magic is real.

Also, if he doesn't keep killing people, he's going to die.

There have been points in his life when he would not have considered this a downside. But — not anymore, he thinks.

Besides, his work is too important.

Killers don't walk free often, but Miyanagi Chinami is far from the only one, even if you don't count people who get prison but not death.

The research suggests that certainty of punishment is the best way to deter crimes. This was a major reason for the legal reforms that ushered in the new system. But 99% is not 100%, and he wants it to be 100%.

He makes a list, starting with the cases he knows about. He fills it out with criminals from America, Australia, England, anywhere with news in English. He doesn't want to make it obvious he's Japanese. He wishes he could cover up his tracks more, but he isn't willing to gamble on the accuracy of translated news articles from languages he doesn't even speak.

He doesn't want to repeat the same method he used for Miyanagi. Anything that links back to him is a vulnerability. The notebook treats heart attacks as default; that should work well enough, at least. If he times them for just after midnight every day like clockwork, the pattern should be obvious enough to make it clear that murders will not go unpunished.

...If he times them for just after midnight that's a big clue to his timezone. He times them for just after midnight in Los Angeles, instead.

He kills one every day, for now. He doesn't want to run out of legitimate target options.

They're murderers. They're just getting what they deserve. 

(He has the same nightmare every night, but now when he wakes his hands crawl with the sensation of imaginary blood.)