Nanami Neiro

Nanami Neiro is an 8 meter tall 11th grade student. She appears at the school to give Chieri a piece of her mind and become a rival. She became bigger before Chieri did so she's technically her Senpai. The department also tested all of their giant-girl-proof technology out on her by way of trial and error, meaning her life wasn't as good as Chieri's when growing up.