Keiko (ケイコ) is a gorgeous college student who tutors high school students, who are studying for their entrance exams.
She used to have short hair and wear glasses. Now she's a gorgeous woman with long hair.
2 years ago, she pushed herself above and beyond into studying for her college entrance exam, and eventually her body wore out, causing her to miss her exam that year. She passed her exam the next year, but as she harbors a strong feeling of regret for not having rested, a disembodied spirit arose from her trying to lull students she’s been trying to tutor into falling asleep, to keep them from overworking themselves. When one of her student from Sankai High called Manabu Ochiai seeks Rinne's help, her problem is discovered and resolved.