Mari Nishinomiya

Mari Nishinomiya (西宮 まり, Nishinomiya Mari) is Mahiro Oyama's homeroom teacher at Yotsuba University Affiliated Junior High School. She also acted as Mihari Oyama and Kaede Hozuki's homeroom teacher when they were in middle school. She is voiced by Rin Mizuki in the anime series.

Appearance
Mari is a middle-aged woman with long hair that she keeps together in a low ponytail. She wears thin, low-hanging glasses and a loose-fitting cardigan on top of a collared button-up shirt.

Personality
Most of the time, Mari is a friendly and respectable teacher. However, she is a stickler for school wardrobe policy and is quick to discipline anyone who violates those rules, no matter how small or insignificant they are. She has sent Mahiro Oyama home multiple times for violating said policies (once for wearing lip-gloss, and another time for wearing purfume). She also once sent Kaede home for doing something similar.

She does this out of habit, and even once commented on Mihari's outfit when they met during Parent Visitation Day. She quickly backpedaled though when she remembered that Mihari wasn't her student anymore.

Despite her strict attitude towards dress codes, Mari is secretly a major fan of cosplay. She was enthusiastic when her students chose a maid cafe for the school cultural festival due to the fact that they would be making all the maid outfits by hand. She also attends conventions in her spare time cosplaying as popular characters, and is so good at it that those who know her aren't able to recognize her. Mahiro and Miyo ran into her by chance at Lily Garden 39, where Mahiro asked her for a picture since she was dressed as a character from Mahiro's favorite anime. Mahiro only realized it was Mari later after holding up the picture when Mari was lecturing. Mari is embarrassed about her hobby, and thus asked Mahiro to keep it a secret once she confronted her about it.

Notably, despite waking Nemu up to ask her questions during class, Mari finds Mahiro to be so adorable when she's asleep that she doesn't wake her up. She's done this at least twice when Mahiro has fallen asleep at her desk.

Early Life
Mari acted as Mihari Oyama and Kaede Hozuki's homeroom teacher when they were in middle school. She claims that she had just started off the position back then, but it did not stop her from reprimanding Kaede when she violated the school dress code.

Etymology

 * The name Mari means "real, genuine" (真) (ma) combined with:
 * "reason, logic" (理) (ri).
 * "village" (里) (ri).
 * The name Nishinomiya means "west" (西) (nishino) and "palace" (宮) (miya).

Manga

 * Mahiro's First Day
 * Mahiro and Conversation
 * Mahiro's "Something"
 * Mahiro Pretties Up
 * Mahiro's Big Secret (Part 1)
 * Mahiro's Big Secret (Part 2)
 * Mahiro and the School Physical
 * Mahiro and the Perfume
 * Mahiro and Visitation Day
 * Mahiro and the Parent-Teacher Conference
 * Mahiro, the Sun, and the Northern Wind

Anime

 * Mahiro Goes Back to Middle School