いる
to need, to require
The part everything else hangs off, out of 必要. The same いる as being there, except that this one is about whether it has to be. Walk in with no booking and they seat you anyway: いる.
Same reading as いる, to exist, and usually written in kana, so context does the work. It takes が: お金が要る.
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Emaki is not affiliated with, or endorsed by, Kaishi 1.5k or its authors. The word, reading and meaning come from the Kaishi 1.5k deck, used with their permission. The mnemonic, the note and the kanji breakdown are original work, published under CC BY-SA 4.0.