The brilliance of the Momo/Shiina dynamic lies in how they handle grief. Yuasa uses the supernatural element—singing a specific song to summon a spirit in the water—to explore the concept of "letting go." Shiina’s arc is about learning to stand on her own board without Momo physically there to stabilize her, while Momo’s arc is about finding a way to protect her even from beyond the veil.

Momo Shiina (椎名もも) is a Japanese actress and former child idol who rose to prominence in the early 2010s. Born on August 6, 1997, in Tokyo, Japan, she built a multi-faceted career spanning gravure modeling, television variety shows, and film.

: She has appeared in various Japanese media productions, including roles listed on IMDb.