While true that the term originates from Japanese, it’s important to note that emoji is a loanword that has been adapted into english by changing its pronunciation subtly, and replacing its spelling with a phonetically similar one in an alphabet not used in Japanese.

This is similar to when words and phrases are used without much adaptation in the middle of sentences that are otherwise in a different language. There’s a certain je ne sais quoi about English and how it mixes loanwords (such as “calque”), calques (such as “loanword”, where individual parts of the word are translated then recombined) and entire unchanged terms (such as “je ne sais quoi”) freely, and to varying degrees depending on where you are and who you talk to.