Memory
They're sitting together, those of them who are left, remnants of a lost age. An age when legends came to life and the now mythical ten tails was a tangible threat.
What was once fifteen is now ten. They sit there organised by their former genin teams with unopened bottles in the places which would have been filled by the deceased, reminiscing about the days of old. The days when they first clashed and enemy's, then became the firmest of allies, knowing there were things more important than petty rivalries.
There are thing's which have changed (namely their hair. The once bright hues were now streaked with silver.) Many were the same. Like their bonds of loyalty and comradeship.
And they remember (despite being well into their sixties) what caused these bond's to form. That for most of them it was hard won, that these bonds weren't just spontaneous.
And they meanall the more for it.