shidou has a nasty habit of pinning you to the wall. or trapping you with his arms on either side of your head. and this even before he got into a relationship with you.
two incidences the both of you recall often: once when he trapped you, you pinched his nipples making him yell and cover his chest right where it hurt. he found that amusing nonetheless.
the other time he did it again, you just faced down. he teased you but immediately stopped when he noticed something wrong. he asked if you were alright and you just hugged him tightly. he believes that was the start of it.