Maybe it's my disinterest in Adventure, but I feel like I don't have that much to say about this story. Though the concept itself is neat. As in that when you actually are about to win a battle (a clear victory, not this sacrifice thing Patamon has going for himself) you can actually feel it.
Maybe you should add TK and Patamon into the character tags since while Angemon and Devimon are the relevant ones, in the end, Angemon digivoled and is fighting just for TK here.
I like the third paragraph a lot and what it says about Angemon and the conclusion he draws from the power he feels.
What I don't really like is the closing paragraph though. It doesn't resonate with the rest of the text that much. Though it is nice to hear that Angemon knows he'll come back.
On a different note...I think either the posting date you mentioned is off by a month or ffnet is lying. I am confused o_o
...Anyway, good story. It was interesting.