This story is set on Japan. I also used the last name first basis. If you're quite familiar with manga and anime, feel free to skip this. If not, here are the words used throughout the story:

Aniki: older brother

Chan: honorifics used usually for girls, babies, younger children, or those older than the speaker

Fusuma: bamboo framed panels made of thick opaque paper that is used as partition between rooms or doors for closet

Gakuran: school uniforms for middle school and high school boys. The second button from the top is commonly given to someone he likes or asked by someone who likes him in a way of confession.

Half: (Hafu) refers to somebody who is biracial

Hanten: short winter coat padded with cotton

Izakaya: a pub or drinking establishment that also serves food

Kimono: traditional long, wide sleeved robe tied with a sash called obi

Koshien: a baseball stadium in Hyogo Prefecture where the annual high school baseball tournament is held

Kun: honorifics usually used for male of the same age

Obi: kimono and yukata belt

Ojii-san: grandfather

Oji-san: uncle but can be used to describe middle aged men  

Okaa-san: mother

Onee(san): older sister

Otou-san: father

Sake: Japanese fermented rice wine pronounced as SAH-kee

Sama: the more respectful suffix than san used for people of higher rank than oneself

San: the most common honorific used to address someone between equals of any age.

Seiza: a traditional formal way of sitting with upright kneeling position 

Senpai: senior/upperclassman in school, club, or circle

Sensei: teacher but can also be used for doctor, writer, politicians

Shoji: latticed bamboo panels covered with translucent rice paper that can be used as door, window, or partition

Tatami: traditional flooring made of woven straw. Its sizes differ in each region and usually used to determine a size of the room

Wagashi: traditional confections that are usually served with tea

Yukata: light cotton kimono worn in summer festivals and after bathing in traditional inn and hot spring

Zaisu: chair with no logs but normal chair back