Not all samurai find peace in death, nor do all crabs find the right home.
When a samurai with unfinished quarrels dies in battle, the physical form perishes, but the soul remains intact and enraged. Unable to be freed from this mortal realm by the goddess Umato due to their eternal rage. Until they finally come to accept their untimely death, their soul remains within the very armor they died in.
Young hermit crabs found on the shores of Azuhanto, Tekkan have been known to make a home out of a large variety of objects such as large seashells, barrels, and even sunken totems. But when a desperate crab comes across a helmet of an old samurai, they become hosts for an undying parasite that will continuously grow in size the more seething the trapped spirit becomes.