Iin, Chiyo

伊院知与

She is a first-year student at Ohananomitsu Middle School and Aijou Rentarou's cousin, serving as the class president of her class.

Spoiler

Chiyo is reliable and tidy, traits that led to her becoming class president. However, she dislikes negative things such as rule violations, untidiness, messy rooms, rude speech, porn magazines, and underage smoking, among others. As soon as she sees something untidy, she cannot help but immediately fix it.
When she takes off her glasses, she becomes incredibly anxious and begins crying uncontrollably.
Name/Birthday Pun Explanation:
Iin (伊院) is composed of 伊 (Italy, though it may also refer to 伊呂波, meaning "fundamentals") and 院 (institution, or school).
Chiyo (知与) is composed of 知 (wisdom) and 与 (to participate, or award).
Chiyo's full name, written in hiragana, strongly resembles the second half of the Japanese word for "class president" (学級委員長) in hiragana, referring to Chiyo's position at school.
Chiyo's name: いいんちよ, iinchiyo.
Class president (学級委員長) in Japanese: がっきゅういいんちょう, gakkyuu iinchou.
Chiyo's birthday is on October 1st. This day is also known as 'Glasses Day (メガネの日 Megane no hi)' in Japan because the number '1001' looks like a pair of glasses.