Each banzuke includes each wrestler's full ring name, hometown, and rank is also listed. The highest ranked wrestlers are at the top of the page printed with the largest characters. This is followed by wrestlers in lower divisions, with accompanying smaller characters.
The characters are part of the set of Japanese calligraphy typefaces used towards the end of 18th century of the Edo era. The typeface for the banzuke is Sumomoji (相撲文ĺ—) and it was specifically designed for sumo advertisement. According to this video, the bold strokes in sumomoji are meant to represent the physical strength and power of the sumo wrestlers.
Here’s another example of a really striking Edo-era typeface—Kakuji (角ĺ—) which was used for making seals: