There are a number of Japanese words which, when rendered in Latin script (“romaji”), have an “n” sound that gets translated/rendered as an “m”. A few examples:
Tempura; the first kanji character, 天, is “ten” (although now that I read the etymology of this word, maybe not the best example)
Shimbashi, as in Shimbashi Station in Tokyo; the first kanji character, 新, is “shin”
Shimbun, or newspaper; as above, the first kanji character (新) is “shin”
I’m guessing there are more like this. English-speakers have no trouble pronouncing “n”, so why that sound getting lost in translation?