It seems my younger sister committed adultery. Is it okay if I hit her?

One day, Izumi Minashiro, an ordinary office worker employed at a small tax accountant's firm, is called out by his younger sister Mari, who says she has some kind of consultation. When he heads to the family restaurant where they're supposed to meet, he finds an unfamiliar married couple waiting there. "While I was pregnant, your younger sister had an affair with my husband..." The compensation demanded by the wife comes to one million yen. "My foolish sister is terribly sorry!!" Cleaning up after a trashy affair is not the responsibility of someone studying to become a tax accountant!