[ People assuming that her being small and weaker than they are is why there are things such as untimely deaths that occur in the world.

Okay, so maybe he is exaggerating with that but he knows she doesn't need to be strong to get him on the grounds of she picks her target point wisely. Considering all his various encounters that have happened so far, Masamune at least knows better than to presumptive of anyone and the extent of their actions when it gets them something they want or in a favorable position.

Rin is cute and attractive but so are kunoichi... (well they are attractive, anyway)

This provoking behaviour of hers, though...!]

Heh!? Are you really taunting me about this—why, for a reaction!?

[Unbelievable! ]

Once you get punched in the stomach by a small child without expecting it, come back to me and say that all again with a straight face.

It's cool. I don't need that sort of effort from you, just a safe distance.