Immortal Rain - Yenra Picture Wiki
Immortal Rain (Meteor Methuselah) is a shōjo manga created by Kaori Ozaki. It was first published in the Japanese monthly anthology Wings as Meteor Methuselah. As of September 2007, the current eight volumes have been published in English by Tokyopop, with the rest of the series, when published in Japan, expected to follow. The 10th volume has recently been released in Japan. It's published in French by Doki-Doki.
A young assassin named Machika swears to kill the one bounty her grandfather couldn't get: the immortal Methuselah. But when she goes after him, she finds a clumsy, kind man named Rain Jewlitt who has lost more than he can bear in his unnatural lifetime. Unwilling to admit at first that she likes him, Machika willingly follows him as he waits for the one who made him immortal, still swearing to take his life one day. Their love for each other grows as they battle bounty hunters, a mysterious organization, and monstrous "angels" in order to save Rain and perhaps even humanity.