Rain Jewlitt, known as the Methuselah, is a spaced-out, immortal, 624-year-old man dressed in priest's clothes. He's got eternal youth and a large price on his head ... put there by those questing after the secret of his immortality.
Machika Balfaltin is a tomboyish, energetic 14-year-old girl who, upon the death of her grandfather, sets out to kill Methuselah, the one bounty her assassin grandfather, Zol the Grim Reaper, couldn't kill. Instead, however, Machika ends up being saved by Rain again and again from other aspiring bounty hunters attacking them both.
(Source: Tokyopop)

It’s the summer when Natsuru is 11. Ever since he’s turned one of them down on Valentine’s Day, the girls of his class have been constantly ignoring him. This changes just before summer break, when Suzumura, the tallest girl in the year, suddenly talks to him. Later, Natsuru meets Suzumura again outside school and finds out she has a secret…

A miniseries prequel about the encounter between Rain and Zol.

This is a prequel to Immortal Rain set before Machika's birth. Machika's grandfather Zol, who works as a bounty hunter by the name of Grim Reaper, encounters Rain, who turns out to be Methuselah, the most wanted man in the world.
Why did fate bring these two men together and what is hidden behind Rain's clumsy and kind personality?

The title story, “The Mermaid Prince,” told in three chapters, is a coming-of-age story set in Okinawa. The boy, Mugi, has a fascination with mermaids. He moved in from Tokyo when his sister got married to a local man, and doesn’t quite fit in. On the day he met the girl, Madori, she was just coming to terms with her new family situation. His thoughtful gesture made her view him as her Prince Charming.

In the second story, “Snowy Day,” a homeless father and son take refuge from the snow in a library. The librarian soon finds out there is more to them than meets the eye.

The third story, “Ametsukigahara,” is a two-parter about a girl named Akari. There’s not much she cares about in this world, except maybe her friendship with Fumika, who’s afraid of boys. But then Fumika gets a boyfriend, and something happens that makes Akari even more jaded than she already was.