Zekana said: Thinking about it logcially, Suika IS an Oni and with how powerful they say Oni are, i would assume she would be incredibly buff like this.
Strength and pure muscle mass aren't directly correlated, especially when dealing with the supernatural. Suika having the physique of a child makes is all the more impressive that she can lift an entire mountain. Alternatively, one could imagine that she is actually 50ft tall but shrank herself and her muscle-mass/strength remained at the at the same power as if she had muscles larger than a cow despite her small stature. Also, she does have power over density.