that is a really good masaje or she is just Sadomasochist

I'm thinking the later...

Minna's got stress. Lots of stress.

The Big One. It's here.

jajajaja XD. Tha is the super massage o.oU

Att: Aiyane

The artist is depicting how much strength you need for an ACTUAL massage. Some people have backs so bound with stress that it feels like concrete.

What was Mina's special power again?

Spatial vision or something