Does anyone know how to draw the abdominal muscles of a naked man bathing in a hot spring in the anime version? It’s a vague one. Don’t call me obscene.

My suggestion is that you must understand the anatomy of abdominal muscles and copy it several times. When you just look at it and draw it, and then use discontinuous lines to outline the shape, you will have a vague feeling. In fact, there is There are many anime pictures for reference, but the hard knowledge of anatomy is something you need to understand if the author is serious about drawing.