New Earliest Emoji Sets from 1988 and 1990 Uncovered
blog.emojipedia.org
blog.emojipedia.org
https://en.wikipedia.org/wiki/Emoji
So it's going off ecosystem-ness (i.e. it came from Japan!)
But, yes, they're emoji because they were created and named in Japan. The IBM set serves a different purpose and exists in a different context. But, they are both living happily alongside each other in Unicode.
漢字 itself originates from Chinese, where it is pronounced hànzì in Mandarin and hon3 zi6 in Cantonese. It is also used in Korean, where it is pronounced hanja.
In Chinese, 絵文字 is orthographically borrowed as 繪文字 (traditional) / 绘文字 (simplified) — 繪, 絵 and 绘 all being alternate renderings of the same character. It is pronounced huìwénzì in Mandarin and kui2 man4 zi6 in Cantonese, according to the etymology of its constituent characters. In Korean it is borrowed phonetically as 이모지, imoji.