Risuko Sasakama is a Tokyo-born Japanese idol signed to DearStage in Akihabara. Standing 160 cm tall, she's best known for being the singing voice of Mizuki Kanzaki and as a member of STAR☆ANIS.
Her voice is pretty distinctive—fans often note how dramatically it shifts between different songs. The contrast is especially noticeable when you compare tracks like "Midnight Skyhigh" or "Thrilling Dream" to her other work and anime insert versions (though those first two songs stay more consistent with each other). It's one of those things that makes her instantly recognizable once you know what to listen for.
Beyond singing, she's into acting as well, and has an unusual special skill in backwards skipping. You can find her on Twitter at @risukosasakama.
Content compiled by AnimeList.moe from publicly available sources.