One wonders about the medical implications of an immortals blood...
Everyone becomes immortal but only while the blood is in their system. Some begin to gain magic while those most unfortunate lose themselves and mutate horribly into beasts. A coalition is formed to hunt these pitiable souls but in time even the hunters succumb to the blood of the immortals.
Why are you so hot blooded!I won...
by 100ml...Go donate some blood then!I'm already at 1000ml...Humpf...
I can double that...I'm at 2000ml...
How's it going, Kaguya...Kaguya...?