A petite high school junior standing at 144cm. She is characterized by her large, bright eyes and short blonde hair. While she is bright, social, and has a caring big-sisterly side, she also has a short fuse. Because she has been teased with the pun "Seina Chii is tiny" since she was little, she explodes with rage whenever she hears it. Despite her small size, she has excellent reflexes and is the ace of the basketball club. She is best friends with Iyo Oki. Their height difference is a staggering 41cm.