Board Thread:General Discussion/@comment-26849575-20160315015552/@comment-27701762-20160315024709

Fair enough.

There are two possible responses:

One is that the human soul that gains EXP does not retain that power once the human dies. So when the previous humans die, their "soul power" is reset to "one human soul." So even if they gained EXP, then that wouldn't matter once they are killed.

The other is that these are two entirely different forms of power, which can be roughly equated, but not directly transferred. So while Frisk/Chara gets more powerful, until Chara becomes as powerful as if they had the equivalent of X human souls, it does not mean that once the soul is removed from the body and absorbed by a monster that monster would in turn gain the equivalent of six human souls.

Of course, there are a few other possibilities. Maybe EXP does stay, but there's no way of calculating the power. Maybe 20 is simply a magical number in LV terms, so that a soul with LV 1 and a soul with LV 19 are the same. Maybe the previous kids did indeed die without gaining EXP.