TLDR: Older Brother

A little more detail if you like-
Onii can end with 3 different Japanese honourifics, -San, -Chan, or -Sama.
-San is the basic ending for the basic big bro.
-Chan is a more compassionate ending for Onii if you really love your big brother and feel emotionally attached to him greatly
-Sama is a bit of a formal ending for big brother, nothing too special.

My Onii-San is a cool bro
I really love my Onii-Chan!
Yes he is my Onii-Sama

Onii-Chan by Rywen March 10, 2015

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Onii-Chan

Onii-Chan means "Big brother" in Japanese. Most people assume it's a mating call of some sort because of hentai but no that's just hentai. Lots of hentai has incest.

"Onii-chan! Drive me to my friend's house!"

Onii-Chan by RigsSaysGoodbye May 4, 2018

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Onii-san

Onii-san is Japanese honorific, meaning 'Older Brother'. It is used within both families or close friends. The 'San' is used for a sign of respect by others within the family or outside of the family and the 'Onii' is to signify someone as a brother.

"Onii-san, come over here and eat with us."

Onii-san by Azeiox December 13, 2014

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