[Jaydelart]

There are many, but here are a few:

-- Utada Hikaru -- "Stay Gold"


-- BoA -- "Do The Motion"
(note: She's actually Korean, but has established herself as a Japanese artist)


-- Maaya Sakamoto -- "Kaze Machi Jet"
(note: The song starts at about 0:33)


-- Sowelu -- "I will"


I posted these songs particularly for the quality of the vocals.
I wasn't sure of your taste, so I tried to make them somewhat diverse, in terms of sound, range, genre, etc.

As for male singers... I don't listen to a lot of slow songs by males (or -- at least, not anything really vocally demanding). I'm sure someone else might be able to tell you some good male vocalists.