I also think that the text is mistranslated and the whole chapter is consentual based and yes if hiiragi wanted to stop he could have punched or hitted shizu like when shizu was asking about whether he should stop or not that time hiiragi hitted him while stating that he should not plus hiiragi is not defenceless...plus i think that hiiragi was relieved at the end so everything is fine and cool ٩(๑❛ᴗ❛๑)۶..and i think shizu laugh/smile while showing his teeth so yeah everything is gud...