Cavematsu-san 2 / Matsuzou and Matsuyo

The prehistoric sextuplets return, partaking in dangerous sports. Later, in modern day, noticing their father acting strangely, the brothers discover that he is worried that there's not enough spark in his marriage. Feeling he should return to a more innocent time, the boys give their old man a masterclass in being a virgin, albeit with no success. After embarrassing himself in front of his sons, Matsuzou considers a love potion from Dekapan, but is this really the best way to patch things up with the love of his life?