Responses
Pretty sure that's just his thumb... I think they just put too much tone on the thumb joint and it makes it look like 2 instead of 1.
ahhh-I'm sorry, because of the position and the shape the tip of the thumb appeard to me like a 5. finger.
the fist from kadowaki-san has one finger two much on the second panel...
http://www.mangago.zone/read-manga/porno_of_yankees/uu/2b4f95a054aeb94f9453f12a291314a7_chapter-7/pg-7/