[Fate X Katekyo Hitman Reborn] This Mukuro Rokudo Has Terrible Luck

"Are you my servant?" The bowl-cut boy gave a dry laugh. "I never thought a pineapple relic could summon a Heroic Spirit."

Hibari, hit by the Ten-Year Bazooka: "..."

Long story short, it's all the Vongola's fault.

The pairing is Gilgamesh: all versions of him, young and old, Archer and Caster.