腎 is a Japanese kanji written with 13 strokes, listed here under the keyword “kidney”. It is built from 月 (month) and 臤 (loincloth). In Remembering the Kanji by James W. Heisig it is frame 916.
On KumiJi Glyph Explorer, open the parts search and type “month” + “loincloth”. 腎 is among the results, together with every other character containing the same shapes.
Open 腎 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.