Most English people wouldn't know what "kanji" means so the people who would be using the word would probably mostly be familiar with Japanese to some extent and would say "two kanji". Most English people would say "two ninjas" or "two samurais". The Japanese word "nunchaku" can be pronounced "nun-chuckers" in English, as if someone were throwing nuns around, or "nun-chucks", so the first syllable would rhyme with "run" in a standard British accent (though not in a northern English accent).

Japanese words seem to be partially assimilated into English. The online Collins dictionary gives tsunami with the standard +s suffix for plural. tsunami > (pl) tsunamis It gives two plural forms for ninja and kanji. ninja > (pl) ninjas, ninja kanji > (pl) kanjis, kanji Finally, it gives samurai without the +s plural suffix. samurai > (pl) samurai

I think what Matt is saying is that it is possible that you might hear "two kanji" because the word "kanji" has not been fully adopted into English yet, and therefore it is most likely that anyone using it would know Japanese well enough to know the Japanese rules about plurals. We have taken lots of words from other languages, and in return they have taken some of ours, and this has led to some strange anomalies. For example we have taken "panini" from Italian. In Italian it's a plural meaning "bread rolls". The singular is "panino". But in English it describes what we imagine to be a specific type of Italian style sandwich, so we say "a panini" or "two paninis". Likewise, Italians have taken English words such as "film", which is singular in English, and used it as a plural by saying "i film". And in the same way we've anglicised Japanese words, and those that are more well known have versions that sound like English plurals... but maybe that's not happened yet for "kanji"... but it will happen