A second year at Mihama Academy, and daughter of "East Beach Railway Express Group" tycoon Michiaki Sakaki. Yumiko was the first student enrolled at Mihama Academy. Due to her blunt personality and troubled past, she associates poorly with strangers.
Always trying to be alone, she hardly meets with the others. She always carries a box cutter with her and use it to threaten others when she's getting angry. She reads so many books that she’s called a "Bookworm," especially, mystery novel is her favorite. Although she's such a lady, she changes completely in meal time. Junk foods like a cup of fried soba noodles is her favorite dish.
Her representative fruit is the grape.
