You know, I've never really known how to reply to this thread, despite liking numerous other artists.
As for other Japanese bands and singers, I'm mostly interested in Perfume, Akiko Shikata and ClariS, although I'm also a fan of Mami Kawada, Kyary Pamyu Pamyu, Maon Kurosaki, Kaori Oda, Kanako Ito, KOKIA, Eiko Shimamiya and Etsuko Yakushimaru. Other Japanese soundtrack composers I'm a fan of alongside Yuki include Susumu Hirasawa (Paprika, Berserk), Hiroyuki Sawano (JoJo's Bizarre Adventure, Kill la Kill), Shiro Sagisu (Evangelion), Kow Otani (Shadow of the Colossus), Akira Yamaoka (Silent Hill), Yoko Kanno (Ghost in the Shell: Stand Alone Complex), Keichi Okabe (NieR, Drakengard 3), Shoji Meguro (Persona 3/4) and Toshio Masuda (Mushishi).
Soundtrack composers in general are a huge part of my music tastes outside of Japanese talent too, I'm a pretty big fan of film composers like Clint Mansell's works (Requiem for a Dream, The Fountain), John Carpenter (Halloween) and Vangelis (Bladerunner) but a lot of my interest is in scores for videogames, most notably the works from Chris Christodoulou (Risk of Rain), Alexander Brandon (Unreal Tournament, Deus Ex), Darren Korb (Bastion, Transistor), Danny Baranowski (Super Meat Boy, The Binding of Isaac), Magnus "Souleye" Palsson (VVVVVV) and Frank Klepacki (Command & Conquer, Universe at War).
I also listen to a considerable amount of non-Japanese music, though. I'm a pretty long term fan of various forms of metal mostly interested in melodic death metal, doom metal and post-metal. Favourite artists there include Agalloch, Insomnium, Amon Amarth, Draconian, Machinae Supremacy, Cult of Luna, The Angelic Process, Iron Maiden, Anathema and Mourning Beloveth, most of which fit into the aforementioned three genres, although some are better classified as heavy metal, folk metal and drone/shoegaze.
As for the rest, I listen to a variety of genres. Sometimes I like rock, others pop, others jazz, or electronica, or post-rock. 65daysofstatic, The Cure and Perturbator are personal favourites outside of soundtrack or metal works, although I'm also a pretty big fan of Garbage, Warpaint, Florence + the Machine, Kubbi, earlier Placebo, Mono and numerous other artists. Safe to say my tastes are pretty wide and I haven't even scratched the surface with this post, really. I do have a last.fm
here, if you wish to look further.