I love Yui. Like her voice and her style of singing. I know Ikimonogakari but dont remember how they sound. Never heard the other one though

Other artists I like:
-Mr. Children (they have great songs, Sakurai successfully conveyed his emotion through the songs)
-Spitz (they're great! Their songs are easily lovable, some are all-time best IMO)
-Sukima Switch (their ballads can make one cries sometimes, eventhough you dont know what they mean)
-Suga Shikao (Somehow I love his voice, and some of his songs are very enjoyable)
-Shiina Ringo/Tokyo Jihen (Shiina ringo is a genius! I love really her songs and her band)
There are many others, but the above endures in my playlist