I've been wondering, why is "how are you?" correct and commonly used instead of "how is you?" Since "is" is singular and "are" is plural and "you" is referring to an individual. An explanation will be appreciated.

Thank you, tutors, for sparing your time reviewing these questions and answering them.

4 answers

"You" is used both as both a singular pronoun and a plural pronoun, as in meaning a group of people (students, family, etc.). Custom of centuries is to use the plural verb form, I suppose to avoid confusion. It seems to be one of those things in our language that there is no good reason for, except that's just the way we do it.
Thank you tutor Reed for answering my question with a simple explanation, much appreciated.

But, one more question, is it correct to use "is" after "you" when talking to an individual? Or will it be deemed as incorrect or abnormal?

I think you already answered it in your explanation, but I'm just checking or I'm just slow to perceive and conceive that using "is" after "you" when talking to a single person is correct.
No, it's not correct to use "is" with "you."

You are smart.
You are a wonderful person.
Thank you, tutor, Ms. Sue, for concluding that using "is" with the pronoun "you" is incorrect. Also for flattering me, despite knowing me. It pleasantly surprised me because I don't often receive compliments.