Kei Kusanagi&#039;s elder sister.     ~!In a flashback which is shown during a critical &#039;standstill&#039;, it is revealed that Kozue was a very bright (though possibly mentally disturbed) girl who felt that human emotions were the cause of much suffering in the world, and sought to escape them by committing suicide, which Kei had had the misfortune of witnessing. The trauma of having done so and the guilt that he had felt at being unable to prevent it led to his first &#039;standstill&#039;.!~    (Wikipedia)  

Kusanagi Kei, a high-school student living with his aunt and uncle, has an encounter with a female alien. This alien is revealed to be a new teacher at his school. Later, he is forced to marry this alien to preserve her secrets. From there, various romantically-inclined problems crop up repeatedly. 
(Source: Anime News Network)

Wife of voice actor [Yuji Ueda](https://anilist.co/staff/95058/Yuuji-Ueda)

__Non-anime roles:__
~!Alex in "Totally Spies!" (animated TV series) (Japanese)  
Bimba in "Breath of Fire III: Drama Album" (Drama) (Japanese)  
Kakurine in "Eretzvaju (Evil Zone)" (VG) (Japanese)  
Mag Launcher in "Evolution 2: Far Off Promise" (VG) (Japanese)  
Majic Lin in "Majutsushi Orphen" (VG)  
Meredy in "Tales of Eternia" (VG) (Japanese)  
Meril in "Odin Sphere" (VG) (Japanese)  
Momoko Ando in "True Love Story 2" (VG) (Japanese)  
Pai-Siang in "Galaxy Fraulein Yuna 3: Final Edition" (VG) (Japanese)  
Pai-Siang in "Galaxy Fraulein Yuna 3: Lightning Angel" (VG) (Japanese)  
Ruri Hoshino in "Super Robot Wars Impact" (VG/PS2) (Japanese)  
Ruri Hoshino in "Super Robot Wars MX" (VG/PS2) (Japanese)  
Satsuki Yumiduka in "Melty Blood: ReAct" (VG) (Japanese)  
Tamami Konno in "Tokimeki Memorial Girl's Side" (VG) (Japanese)  
Xiaomu in "Mugen no Frontier - Super Robot Taisen OG Saga" (VG) (Japanese)  
Xiaomu in "Namco X Capcom" (VG) (Japanese)!~

Kusanagi Kei, a high-school student living with his aunt and uncle, has an encounter with a female alien. This alien is revealed to be a new teacher at his school. Later, he is forced to marry this alien to preserve her secrets. From there, various romantically-inclined problems crop up repeatedly. (Source: Anime News Network) 
Note: 
-The title was never "- sensei," the Japanese characters phonetically spell "teacher". 
-The chapter count includes one extra chapter.

Kozue Kusanagi