Second year junior high school girl Hana Nono wants to be a cool big sister. Her first day at her new school gets off to a rocky start, but she meets some nice people and is looking forward to the next day when a mysterious baby named "Hug-tan" falls out of the sky along with her hamster caregiver Hari. Hug-tan is pursued by the evil Clias Company and its monsters that want her Mirai Crystal. Soon, Hug-tan is attacked but Hana's desire to protect the baby creates a new Mirai Crystal and she transforms into Cure Yell. Hana learns that the Mirai Crystals have the power to create tomorrow and if the crystals are taken, everyone's future will disappear.