Katakura Kippei plays the part of a typical high school playboy, dedicating his days to pursuing every female in sight while struggling to take on any form of responsibility. However, his priorities change suddenly when he is abruptly tasked with being the primary caregiver for his 5-year-old cousin. His aunt, Miyako, has vanished, leaving the vulnerable Yuzuyu behind. With Kippei's inexperience in childcare and Yuzuyu's emotional struggles, their journey together is bound to be a rocky one. This story is adapted from the manga by Maki Youko.