Haha I laughed out loud at Shiki. That poor undead is too weak for this group and is genuinely scared of both his 'sisters'. Not only is his ego continuously being trampled on, his common sense of strength is also constantly questioned. Compared to normal strong people, Shiki as a Lich was powerful, but compared to Tomoe and Mio who are like demi-gods and also further after being boosted by their 'Waka', the realm of power is completely off the scale.
Since both sisters take out their frustrations on him since he is a helpless undead. He has constant shivers when their bloodlust seeps out. Haha.