lol, sometimes i was thinking about asking that question, but i forgot about it.
Anyway here are yaoi where guy step on other guy's crotch or something similar (by similar i mean having boner when guy touches another guy).
http://www.mangago.zone/read-manga/ore_ga_neko_wo_kaburu_no_wo_yameta_riyu/ seme touches uke and uke gets boner.
http://www.mangago.zone/read-manga/ichimai_goshi_fetish/ sry another manga without foot.
http://www.mangago.zone/read-manga/nakasenaide_ne/ finally yaoi that you've been waiting for.
http://www.mangago.zone/read-manga/jackass_sawatte_ii_tte_dare_ga_itta_yo/ and another one.
http://www.mangago.zone/read-manga/takashima_kouichirou_no_risou_no_koibito/ uke kind of touch seme's crotch in last chapter.
http://www.mangago.zone/read-manga/risou_no_koibito/
I think there's a scene in here that the seme kind of does that. But if not, the seme is kind of cruel to the uke and the uke is emotionally inferior and stunted.
i need Yaoi where the guy steps on the other's crotch ?? idk i Can't find a tag like that