急 is a Chinese hanzi, listed here under the keyword “quick”. It is built from 刍 (mow) and 心 (heart). It appears as a component in 3 other characters in this index.
On KumiJi Glyph Explorer, open the parts search and type “mow” + “heart”. 急 is among the results, together with every other character containing the same shapes.
Open 急 in the interactive kanji search
to expand every part down to its smallest pieces, add your own names and mnemonic stories,
or search for other characters by their parts.