Captain Choromatsu invites an interesting detective onto an increasingly dangerous murder case to ease the tension of the crew. / Totoko wants to be a popular idol, but reality is so cruel.

The prehistoric sextuplets fool with nature for the last time. Several thousand years later, in a parody of Romance of the Three Kingdoms, Emperor Osomatsu and a group of bizarre generals attempt to take over the country. Meanwhile, in the real world, Osomatsu joins Todomatsu at a mixer, struggling to keep his perverted instincts in check.

Karamatsu tries to take on various requests from everyone to look like a reliable brother, only to take on more than he can handle, so Choromatsu tries to teach him how to refuse. Totoko begins working at a company, proving to be a handful for her superior Todomatsu. Later, a pair of seiyuu attend a dubbing session of an episode of Mr. Osomatsu, witnessing how the sextuplets do their work.

Ichimatsu becomes paranoid when lucky things happen to him all day, so he and Jyushimatsu try to punish themselves to balance things out. A lovey-dovey couple go to a hot spring inn that's haunted by a zashiki-warashi named Osoma.

In the 1960s, Iyami comes across a blind flower girl named Okiku and, despite being poor himself, tries to help her raise money for eye surgery.

After Dekapan becomes president, his secretary Todomatsu tries to keep him from pressing the Big Red Button. Iyami attempts to pull off a sham ventriloquism scheme by having Chibita and Hatabou act as his puppets. On Valentine's Day, the brothers try in vain to get some Valentine's chocolate from someone.

Matsuzou becomes hospitalized, leading the brothers to seriously think about their lives and get proper jobs to support their family. A chance meeting with Totoko sets Osomatsu's mind straight...