The Kamikaze pilots clipped their fingernails and put them in a small box. The box was presented to their commander prior to their leaving for the last mission. This box was then presented to the family of the pilot upon completion of the mission. During the pilot's funeral the box was the proxy for the body that would never return.
In return for their fingernails the pilots were given a recent Japanese invention called methamphetamine, a sort of bottled bravery. This insured that they could stay awake for the long sorties over the Pacific and they wouldn't need food. The other helpful effect was that upon arrival at the target they were so tweaked some almost certainly believed that they would survive the attack without a scratch and return home to their families and the glory of the Emperor.