Well... Japanese uses a moraic system to measure their syllable clusters... this basically means that all sounds in Japanese must be the same length... for instance, よ (yo) must be the same length as ス (su), when you speak them out loud.

Now to understand what this has to do with what were talking about before, you have to know that ん (n) is also one of these sounds that must be the same length as all others. So in the word "みかん" (mikan), you have to spend just as much time pronouncing the 'n' and you do the 'mi' and 'ka'.

OK, so it's important to know that 'n' takes up a full sound in Japanese (while English doesn't use that moraic thing I was talking about), now you can understand why Japanese doesn't have the same rules for word (and syllable cluster) formation as English does. For them, the word 'tenpura' takes up five sounds 'te.n.pu.ra' while in English, we make it into only three syllables: 'tem.pu.ra'.

But why does English make it into only three syllables? Well we take the original word: tenpura, and say "oh no, 'n' and 'p' can't be next to each other because it would take too long to pronounce. We'll make 'n' into 'm' because both 'm' and 'p' are pronounced the same way". Think about it- a 'p' is just an 'm' where you push air out of your lips*. Pronounce tempura the English way and then the Japanese way (ten-pura) and see which is easier. I don't know about Malay or Indonesian or whatever you speak, so maybe the Japanese way seems more natural, but to a native English speaker it isn't.

Japanese doesn't have a rule like this because of that 'syllable length' thing, and they see 'n' as perfectly fine in this cluster.

I guess I could have explained the better, but I would need to be in person, and have some charts and graphs ahahha. There's even this Japanese song where they try to teach kids the 'English' way to pronounce words.. that's where I came up with the tempura example.

Ah, so one more thing. Tempura is a native Japanese word that English made into tenpura. But what about 'Conbini'? That comes from (I'd like to think..) the English word 'convenience'. The thing is, Japanese doesn't have a natural 'v' sound (actually few langauges do), so when they can, they like to turn 'v' into 'b'. So Japanese turned "Conveni' into 'Conbini', and then because of our English rule, we turned 'Conbini' into 'Combini'!!! Pretty freakin' crazy!!!


*in some languages, like Korean and I think Hindi, there are two ways to pronounce a 'p', depending on how you use the air when making the noise. This makes languages like Korean really difficult for some people!!