I'm just wondering, since Garai died before the time split happened... and Radius clearly remembers murdering him... when he found the Masamune back in El Nido.
Gairi died "15 years ago". The Dragoon's also were fighting on the "mainland" 15 years ago. The only place we know of where there was fighting "15 years ago", or in 1005, is during Guardia's fall. The scene where Gairi died, looks like Divine Dragon Falls, right? Does it not also look like the place in Denadaro Mts where you find the Masamune? A waterfall with a cave next to it? The creators in CC reused models and sprites for different things in the game to conserve memory. Since Divine Dragon Falls and that are of Denadaro Mts look very much alike, its not a huge jump in logic to say that the map was reused, and Radius did in fact kill Gairi at Denadaro.
Also, does anyone have a screen shot of the Divine Dragon Falls? Its been a while since I've seen it, and I think it would show the point a bit more.