A big thanks goes to http://www.rpgclassics.com
for VERY useful and rare information.
There's been a lot of confusion between Suikoden gamers about saving Nanami and achieving the best ending. There are many sources out there, but of all the ones I've seen (with the exception of rpgclassics, of course), there lacks a very important detail.
My guess is just as good as anyone else's, but I think my situation is the same as a lot of you who's had difficulty with saving Nanami.
Now, a lot of us assume that as we come to the point right before the dialogue, we can remove Nanami's precious equipment and not risk losing anything... Wrong. What a lot of sources forgot to mention was that Nanami's ARM rating "MUST" be above 180. Look like the creators took a lot of logic into consideration here. It makes perfect sense - Higher defense means a better chance of living.
A lot of us gamers don't have this problem because we sometimes don't even consider removing any of Nanami's armor prior to the scene. Hopefully this solves a lot of problems. It sure solved mine.