Brava!  

  First impression - a lovely little miniature, a gentle sweet romance
reminiscent of Joseph Palmer's fics. 

  One question. You wrote:    

On the darkened floor of the laundry floor, glinting in the starlight, were
the Tendo family katana and an empty teacup. 

Beside the katana was Kasumi's hair ribbon.

"Thanks, Kasumi," he thought, laughing softly, taking the teacup to his own
room.

  I'm afraid that I didn't catch the reference.  What did these items
signal to the rest of the household so that they did not interfere?  

                                                                     dml