須 - ought, by all means, necessarily

indispensable; essential; requisite; required; compulsory; necessary

essential condition

unsun karuta; Japanese deck of cards with 5 suits of 15 cards each

essential amino acid

mandatory attribute; required attribute

required entry (e.g. in online forms)

Mount Sumeru (believed to be the centre of the Buddhist world)

Beyrich's slit shell (species of sea snail, Pleurotomaria beyrichii)

beard

Susanoo-no-Mikoto (deity, younger brother to Amaterasu)

small teapot

absolutely necessary