Okusama: Hisokana yorokobi (2000)

The Miyoshi family consists of three members: Reiko (the wife), Sugio (the husband), and Tsubaki (their son). Into this household comes Megumi—Reiko’s niece—who has traveled to Tokyo to take university entrance exams. Tsubaki has a girlfriend named Arisa. Megumi harbors a crush on an upperclassman named Natsukawa, who is himself in love with Arisa; however, Arisa had rejected the uncool Natsukawa in favor of dating Tsubaki. Megumi is nonetheless shocked to witness Natsukawa still pursuing Arisa. Amidst this situation, Sugio’s father, Tokuzo, returns home after being kicked out of his nursing home. The lecherous Tokuzo immediately sets his sights on Megumi...