Is it possible to prevent this character's death?

In Suikoden 2, towards the end of the game

Nanami

was killed, but there's some rumor that she didn't actually die, and that it's possible to "bring her back to life" by gathering all 108 stars; is that true?

Solution 1:

Yes, it's possible. However, in order to do so, you need to do the following:

First, obtain all 108 Stars of Destiny before the battle of Rockaxe.

Next, ensure that Nanami has at least 121 DEF rating. Making sure that she's of an appropriate level and wearing some halfway-reasonable armor should be all that's needed to hit that target.

Then, during the part of the Rockaxe assault where the archers appear and you're given a dialogue choice, choose either option very quickly. (Contrary to popular belief, either choice should work, but you must make a selection within roughly half a second of the prompt appearing.)

At this point, you'll know that you've met the conditions to save Nanami if, in the story sequence after the battle, Dr. Huan asks Shu for permission to speak privately. If this doesn't happen, you may want to reload an earlier save and try the above things again.

After beating the game's final boss, decline to become the new nation's leader.

Travel to Tenzen Pass. During the final duel with Jowy, don't beat him. By far the safest (and quickest) way is to simply choose Defend every time.

Eventually, the battle will end. When Jowy offers to give you his rune, continue to refuse every time. After you do that enough times, you'll receive the true ending, wherein Nanami and Jowy both live.