How?

Still don't explain how his arm go right into her Armor!

hizack123 said:

Still don't explain how his arm go right into her Armor!

I think she did it on purpose...

Oh, you mean she made the armor disappear and reappear in an instant?
That's... quite an interesting thought.

Yuujin-A said:

Oh, you mean she made the armor disappear and reappear in an instant?
That's... quite an interesting thought.

It's obvious the joke is that she's flat chested enough there is a gap in her armor between her tits and the inner surface of the armor.

Hence there being enough space for Shirou's hand to slip in.