Shinigami in Death Note

Shinigami is a grim reaper, the death angel that exist on Death Note series. They have a Death Note to take human's live for expand their own lifetime.

The Shinigami live in Death Realm, that place is very boring. A fun-finder Shinigami like Ryuuku often went down to human realm to get some fun. No human can see them without touching their Death Note before. A Shinigami, or anyone who has a Death Note, could kill the one only with write down the full name in a Death Note paper. It's possible to write down a complex killing way, but it must be written before 6 minutes 35 seconds passed after the name. But, a Shinigami is never though as far as that. They just write down the name and let the one who his/her name had written died by a heart attack in 40 seconds after.

The question: how could a Shinigami know human's name so easily? The answer is on their eyes. A Shinigami eyes could see human's real name and lifespan easily. This ability also could be transferred into human that has a Death Note by make an eye deal with the Shinigami. It cost the half of his/her lifespan. A Shinigami lives forever as long as they could kill human. The rest of normal human's lifespan belongs to the Shinigami who killed him/her. It means that if he/she normally died in 2026, but a Shinigami killed him/her in 2008, so the 18 years will be added to Shinigami's lifespan.