| 高山 ケイト|
|Age|| 15 (Vol 4~5)|
16 (Vol 6~onwards)
|Family||Maria Takayama (younger sister)|
|Japanese Voice||Emiri Katō|
|English Voice||Brina Palencia|
|Anime Debut|| Episode 8 (cameo)|
NEXT Episode 2
Kate has impressive looks, which can be described as a, "matured Maria". Both she and Maria look Caucasian ("Northern Europe" by words of Kodaka). As such, she shares multiple traits with her younger sister: lavender-silver hair, blue eyes and pale skin. She has a well-endowed body. In Kodaka's opinion, she has a sublime, "ideal teenage girl face" and "perfect proportions". It should also be noted that because of these "maturity" traits, she appears older than she actually is. Another distinctive part about Kate's appearance is the beauty mark under her left eye.
Kate has some of the same traits as her younger sister, Maria. She has also been described as "vulgar". She doesn't seem to mind farting, scratching her butt, burping, and telling dirty jokes in public. Outside of these habits, she is quite composed and serious, Kodaka even got confused of her actual age (in sum with her looks and she gave off impressions of someone older). She has an eccentric viewpoint on life, especially on religion (which in her position is practically the same), thinking that Christianity is a "rebellious" religion. However when it comes to food, Kate completely turns into her little sister, her eyes glow and she falls into a simplistic manner of speech, which is quite similar to Maria's.
It is shown that Kate actually cares a lot about her younger sister Maria, constantly worrying about her and seeing whether or not she is well or happy. She is very grateful to both Kodaka and Yozora for signing Maria up (forcing) for the position of supervisor for their club. She has noticed a large change in Maria that she or the other sisters couldn't accomplish as the members of the Neighbor's club had.
It is shown that Kate might harbor a small crush for Kodaka, but it is unclear if she completely let those feelings go because she knew of the status of both Kodaka and Sena's arranged engagement.
- Sister Kate (By the students of St. Chronica's Academy)
- Mother Kate (By some students) 
- Kate-sensei (By Kodaka)
- Old hag (by Maria)
- Onee-sama (By Maria)
- Onee-sabitch (By Maria)
- Poopy Old Hag (By Maria)
- Pooper Trooper
- Big Sister Poop
- Poopy Head
- Dummy Fart Freckles Idiot 
It's currently unknown which position Kate holds, besides being one of St. Chronica's nuns. It can be assumed that she may work as a teacher because of her own words: "...some students call me Kate-sensei". She has a vast knowledge of Christianity, especially its origins and history. Despite this, it's uncertain if she has the same mental abilities as her sibling, but the fact that she holds some position in school and is quite educated in religious studies at such a young age indicates her intelligence.
She also has the same bottomless appetite if not more gluttonous than that of her little sister's (as on Kobato's birthday she was the one who ate most).
- Like Maria, Kate's surname, Takayama ( 高山 ) literally means "Tall Mountain".
- Also, same as Maria, Kate's surname, Takayama and her Catholic background may also be an allusion to the famous Christian-Daimiyo during the civil war era, Dom Justo Takayama.
- The meaning of Kate's name in English means "pure" or "chaste". In Hebrew, Kate is interchangeable to Mary, which means "Bitterness". This may allude to how Kate feels sad and depressed about Maria's treatment of others as compared to her.
- Kate and her sister seem to have a great liking for Nikujaga (Japanese Meat and Potato stew).
- In the English manga, Kate is called Keito.
- During Kate's first cameo appearance, she is seen wearing a cross necklace. Later in the series, this necklace changes to one with a key.