Immortality is eternal life or the ability to live forever. It can be a blessing, but also a curse to the person who receives this rare spectacle of a gift. You can stay physically the same, never getting older in appearance, and you can become wiser and more adaptive as time passes on. Death will always evade you, never taking you, and you can do everything you've desired and more. You can meet new people all of the time from different eras of time. The downsides, though, can certainly overpower those benefits you can gain. You outlive those around you, and you cannot pass and be with them in the afterlife. Even if you meet new people, they'll end up passing as well, and you can't do a damn thing to stop it.
This was the case with Eren Jaeger, someone who was born with this 'gift' of immortality. Long ago was his birth, and during the time before he was taught of what he had, he grew up with his best friend, Armin Arlert, an intellectual blonde who loved to be with him. Eventually, they grew to more than best friends, and they spent the rest of their lives together-- well, the rest of Armin's life. Soon enough, the blonde passed while Eren could not.
Centuries passed the brunette for the longest time, and every century seemed to bring a familiar male, a reincarnation. Near exactly like the one he had met and married the first time, every result was different from their first encounter. This reborn version of the male couldn't ever remember any of their past lives, and nothing happened more than crushing, maybe a relationship before moving on. The closest time they ever got to having what was originally had was ended with a terrible accident, resulting in an extremely early demise of the brunette's lover.
After over a thousand or so years of these incidents happening, he met the tenth reincarnation of his lover. This time, though, he seemed more like the original than any of the others.
The blonde, wearing a fluffy jacket and jeans on this cold winter's day, walked up to the door of Eren's apartment. In his nearly-numb fingers he held a section of the local paper, one which requested for a roommate. As he adjusted his glasses, he made sure he was at the right numbered apartment. "This seems like the place..." Running a hand through his blonde locks, he knocked on the door, hopefully thinking the other was home. He was in desperate need of a place to share with someone, anyone, and this was the only one in his prince range with his terrible job he was forced to work. "Please please be home..."