Musae Koyama is Misae's younger sister. She's 26, perpetually exhausted, and would honestly sleep all day if she could. After her photography boss told her she had no real talent, she quit—and with no income to support herself, she ended up moving in with Shin-chan's family without even giving Misae a heads-up (this happens in episode 562).
Photography is her passion and dream career, but her father wanted her stuck in some office job. When he refused to let her pursue it, they both lost it—he kicked her out, and she fled to Kasukabe to stay with her sister. Those three months were rough. Shin-chan drove her up the wall constantly, though she genuinely cared about him despite getting angry at him regularly.
She's got a good heart underneath it all, but she's got serious anger management issues and can blow up over nothing. She's ambitious about her photography dreams, even if they're mostly still imaginary. Beyond that, she's lazy—eating and sleeping are basically her hobbies—and her room is a complete disaster, which tells you everything about how much she cares about cleaning compared to Misae.
Eventually she picked up temporary work at the Kasukabe Bookstore, and while photographing kids at the nursery, the official nursery photographer noticed actual talent in her work and brought her on as an assistant. That job finally let her move out and get her own place: the Matazuresou, which happened to be the same apartment complex where Shin-chan's family lived.
She's roughly the same height as her sister, though her hair is shorter and a lighter brown with neater bangs. She usually wears pastel-colored shirts—short or long-sleeved—with light-colored pants.
Content compiled by AnimeList.moe from publicly available sources.
