Nagisa Miyazaki

Jiyu Nanohana is an ordinary schoolgirl until she runs across a scatterbrained 300 year old samurai who tells her that she is the reincarnation of Yagyu Jubei. With the help of the "Lovely Eyepatch" she transforms into the legendary swordsman whenever she needs to use his awesome fighting ability, which she needs to do quite often as a rival clan is dead set on conquering Yagyu to satisfy an old family grudge. (myanimelist.net)

Hashiba has an accident and has lost all of his memories. When Fujimori comes to his school as his new roommate, He tells Hashiba that he is called Ran. He and Hashiba both have a split personality which they developed in their youth. (imdb)