Box Kei!(1999)

Fuji Zeze is going to Hakone with her friend Ritsuko to participate in the final auditions of a Japanese idol competition, but in the middle of the mountains, the bus flips over. Too impatient to wait for the search and rescue team, she and Ritsuko, along with three others Mikami Renji, Tsuburaya Hajime, and Kaji Shinju, try to find their way out on their own. But, they soon learn that things are not all what they seem...

(Source: Shogakukan, translated)