Burn the House Down volume 3

Anzu Murata, assuming the false name of Shizuka Yamauchi, sneaks into the Mitarai household under the guise of a housekeeper in order to ascertain the truth behind the fire 13 years ago — a fire for which her mother took all the blame. Selling herself to Makiko, the hard-to-please second wife of her father, Dr. Mitarai, she continues scouring the Mitarai household for clues as she gradually gains Makiko’s trust. Just as she’s on the verge of finding proof that would connect Makiko to the fire, Anzu’s real identity is deduced by Makiko’s son, Kiichi!