Kyūjitai form of 内殻 (“inner shell”)

shell, crust, chaff / husk, hull

an aquatic shellfish (generally limited to mollusks with calcareous shells such as clams or snails, and excluding crustaceans such as shrimp or crabs)

very; extremely / exceedingly; tremendously

extraordinary, unusual

emergency

Solid, hard, firm.

Keeping a material's shape that does not crack or break apart; hard / Keeping one's appearance or facial expression; serious

cinders, ashes / leftovers

shell