Emi is a third year student at Todo Academy. Not only is she Mitsuomi Takayanagi's second-in-command, but she also harbors a deep respect and love for him. She is very concerned about Mitsuomi given his heart condition, and is probably more protective than she needs to be. Since Mitsuomi's still has lingering feelings for Maya Natsume, Emi sees Maya as someone she must defeat (the manga offers readers a glimpse of a strange friendship, or at least, mutual respect).

Being a member of the rich Isuzu family, she works the family's traditional job as the Takayanagi family's inner guard. Two years ago, she served as Mana Kuzunoha's bodyguard and was often responsible for videotaping the various individuals that the Takayanagi family found interesting.

At first sight, Emi appears to be a drop-dead gorgeous girl, and so popular with the male students that she is first on the list "Women by whom I would like to be stomped on by"; however, she is not called, "The Black Blade" for nothing. Her most coveted secret is that she is extremely obese, which she does on purpose so she can use her ability to contort and fold her fat. In these folds, she can hide throwing knives and other various small objects if needed. Thus to the untrained eye when she is fighting, Emi seems to be able to pull knives out of nowhere. This secret is so well kept that only a few people know; Maya and a very shocked Shirou Tagami are the only known people that have been confirmed to have seen her true form, although Shinobu Kagurazaka seems to know about her true body, going by his comments after her defeat by Madoka Mawari.

(Source: Wikipedia)