@sokino: I don't listen to too many Japanese R&B singers, mainly because most of them are females, sound often quite similar, and lean far too much into the Pop category, but there are a few R&B singers I enjoy.
1. KG is pretty good. I came across him from the group "NATURAL 8" which is a group that consisted of a combination of R&B singers and Rappers (now broken off into MAY'S, KG, SHIKATA, and CLIFF EDGE). They have a soulful sound, but most of their music has more of a ballad-esque feel to it. KG's voice kinda reminds me of Keith Sweat. haha
KG 「With You〜君といつまでも〜feat.MAY'S」
KG「きっと、 ずっと duet with MAY'S」
2. JAY'ED is like the Ne-Yo in Japan. He has a soothing voice and has good pronunciation of English (which to me overall makes a big difference in the quality of the song as many Japanese singers fail with pronunciation of English parts in their songs. I think JAY'ED grew up in New Zealand, so that explains why his English is great.)
JAY'ED「最後の優しさ」
JAY'ED「Superwoman」
3. NAO is my favorite R&B singer so far. I found him last year when his first album dropped and now you can find him on L-VOKAL's latest album LOVIN'. He has both vocal and piano talent like Alicia Keys or John Legend. He only has one album out, but that album was so fantastic that I'm highly anticipating his next release whenever that is. Very passionate and moving melodies.
NAO「Paper Moon」
NAO「One Way Feat. Micro」
NAO「ここで待とう」