徐 is a Chinese hanzi, listed here under the keyword “slowly”. It is built from 彳 (step with left foot) and 余 (i). It appears as a component in 1 other character in this index.
On KumiJi Glyph Explorer, open the parts search and type “step with left foot” + “i”. 徐 is among the results, together with every other character containing the same shapes.
Open 徐 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.