Seven rules. Every one of them exists because your mouth is taking the shortest path between two positions.
Korean spelling shows you the word. Korean speech shows you what happens when that word meets the next one. The gap between the two is not chaos and it is not something you memorise word by word — it is seven predictable consequences of how a mouth moves.
In this lesson the pronounced form is written in brackets, in 한글. Read both and feel the difference in your own mouth.
The bottom consonant has no vowel to lean on, and the next packet starts with the silent circle — an empty slot. Rather than sealing and re-opening, your mouth simply carries the consonant across.
To go from [k̚] straight to [m] your soft palate would have to be up and then instantly down. It is easier to drop it early — so the seal stays where it is and the air starts going through the nose while the mouth is still closed. The place does not change; only the route out does.
Both sounds are made with the tongue tip on the same ridge. The only difference is whether the air goes through the nose or around the sides of the tongue. Switching mid-contact is fiddly, so the tongue picks one and keeps it.
When you seal a stop and hold it, pressure builds and your larynx tightens. The next consonant starts inside that tension, and tension is exactly what makes the tense series tense. You do not have to do this deliberately — it happens on its own if your final stop is properly unreleased.
This is the most transparent rule in Korean. ㅎ is a puff of breath. A plain stop plus a puff of breath is, by definition, the aspirated member of that family. The two letters merge into the one letter that already means both things.
For ㅣ the front of your tongue is already climbing toward the hard palate. Making a tip-on-the-ridge stop first, then moving, is extra work — so the contact happens where the tongue is already going, and a tip stop at the ridge becomes a blade stop at the palate. Which is precisely the sound ㅈ and ㅊ describe.
ㅎ is friction in an open throat. Sitting between two vowels, your vocal folds are already buzzing on both sides, and stopping the buzz just to make a little friction and then restarting it is a lot of work for very little sound. So speakers skip it.
The last thing worth saying: reading Korean and understanding Korean pull apart for a while. You will be able to sound out words you do not know, which feels strange but is exactly right. Keep reading things out loud even when you do not understand them. The decoding has to become automatic before the meaning has room to arrive.
HanDa corrects every sentence you write or say — in real conversation, not flashcards.