Pride by Gengoroh Tagame.
A favorite scene of mine from Pride. The college student here is kept bound under the professor’s desk in his office while he goes to give a lecture. Then, while he’s gone to class, the professor sends another student—a submissive-ish bottom who this bound guy (formerly a cocky, top-only, big man on campus type) has rebuffed and been crappy to—to fetch something from the office along with another student. The bound guy pictured here recognizes the other student’s voice and nearly loses it with fear and embarrassment, all while desperately trying to remain perfectly still and silent…which just makes the vibrating egg in his ass sound all that much louder in is own ears… >;^)
Ah, Gengoroh Tagame—you put the bar(r)a in embarrasment! Some of my favorite manga-smut!!