I am enjoying this confusion too, I read the raw of this chapter months ago and I didn't understand this part http://www.mangago.zone/read-manga/color_recipe/mi/d_v-2-chapter-6.6/pg-15/ but now reading it... maybe Shou was a little turn on with Fukusuke's feverish face?
I was thinking he was seeing Fukusuke's real face that he hadnt seen in awhile. That intense kinda creepy like ill chain you kinda thing. Cause he's only broken his mask to Shou very rarely.
Fukusuke sure wasted a big opportunity cuz Shou's expression in that page seemed like he was waiting for smt to happen but gonna tsundere face it XD and give in some time if Fukusuke continued... and he didn't ... wanted to see 'em getting hot T_T
ora ora? he was actually dead tired and not just acting? surprising....
does this extra means that shou gets weak from fukusuke's approaching? and he would just give in sometimes to fuku's lies and maybe love him in spite of his real personality? man this is confusing and I love it