(noun) A shy person.

Background: Koi is a homonym with coy, which means shy.

A Koi Fish is a man who gets overly attached to a girl and refuse to leave her alone when she has no interest in him. They generally become psychotic and ruin their friendships because of this. Some of them try to ruin their targets lives.

A type if colored carp . They're way too expensive and a part of Japanese culture.

In Japan during world war II a group of homosexuals got the Koi Fish tattoo on their left arm. Now commonly used in Japan and America as a more verbose way of letting people know their sexual orientation.

While being cracked out of your mind yet still performing. Similar to how a koi fish swim in a small pond cracked out of its mind but still performing.