Gyakufunsha kazoku by Sogo Ishi (1984)
Dark comedy allegoric for japanese society(?), it's about a father who moves into a new home with his family, and starts noticing weird things about them
[spoiler]they're all crazy[/spoiler]
[spoiler]so he decides to cover the home's windows and entrances, and poison everybody as a last resort therapy. This brings the crazy out of all, and after a semi-battle royale, that's as morbid as it is humorous an explosion stops the onslaught.[/spoiler]
[spoiler]they all wake up in a house destroyed by fighting, mother prepares breakfast as if nothing happened, then the father is enlightened and starts destroying the house. Blaming everything on it. The remaining family joins in joyfully. Ending scene is everybody living harmoniously on the street, and hinting at them building a new house[/spoiler]
