Meteor Methuselah, Trinity Blood Recommendations
Both will draw you in with great stories and even greater characters... both deal with longevity, fighting monsters and close friends/siblings becoming enemies.
And you can't help but notice that Abel and Rain are like inter-dimensional twins XD
Both begin similarly... A wandering priest (tall, long light hair, long robes) who happens to be immortal/invincible meets a teen girl who becomes their companion/sidekick. Abel and Rain are both rather air-headed. Soon the stories become obviously different. Both are shoujo-oriented but still action-packed, with great storylines. Trinity Blood is definitely the more violent of the two, though Immortal Rain does have a noticeable about of disturbing content.
1) both are kickass mangas about immortal guys and a girl following him
2) both the main guys are alike ... what i mean by this is that they are both "a little out there" you know what i mean if youve read one of them
1) the girl in Immortal Rain (in my opinion) is MUCH more badass