It's "remains are". This noun, regardless of how we think of it, only has a plural form and takes a plural form of a verb.

It's "remains are". This noun, regardless of how we think of it, only has a plural form and takes a plural form of a verb.

His remains are buried in Oxford.

His remains is buried in Oxford.

Remember, "remains" can be used to speak about the parts of something that is left after the rest has been used or destroyed. It can also refer to the body of someone who has died.

The remains of the building can still be seen.

A police officer found human remains in the area yesterday.

Note that we always use plural determiners and pronouns with plural nouns, like "remains".

Those remains were found in 2019. They were identified as Olivia Swenddal

Follow the same convention with other related words that are typically used in the plural, such as leftovers or ruins.