Mon Mon Mon Monsters
報告老師!怪怪怪怪物! (original)
A bullied boy and his tormentors discover a creature while doing school-mandated community service. Claiming her for their own, the group of kids keep the creature captive, revealing the monster within themselves as her ferocious sister scours the city in search of her missing sibling.
Starring Deng Yukai, Kent Tsai, Carolyn Chen, Eugenie Liu, Lin Pei-Hsin, Tao Bo-Meng, Bonnie Liang, Ti-Men Kan, Chien Te-Men, Bruce Hung
Watch "Mon Mon Mon Monsters" from streaming services shudder-shudder-subscription, shudder (Prime) released in 2017. It's a drama and horror movie, and has a rating of 6.2 out of 10 from Imdb which is usually fine for this kind of movie.