Despite being in their twenties, the brothers have no jobs, ambitions, or direction in life. They spend their days causing chaos, getting into absurd situations, and failing miserably at adulthood. Their antics range from hilarious get-rich-quick schemes to awkward attempts at dating and everything in between, often mocking themselves and breaking the fourth wall with self-aware humor.

While the brothers are mostly the same in appearance, their exaggerated personalities make each one distinct, leading to endless comedic situations as they clash with each other and the bizarre cast of side characters. Some of the recurring characters include Totoko, the object of the brothers' affection, and Iyami, a swindler with his iconic "Sheeh!" catchphrase.

The series is known for its absurd humor, parodying anime, pop culture, and societal norms with no shortage of slapstick, crude jokes, and satire. Beneath the comedy, however, it also touches on the struggles of modern life, such as finding purpose and dealing with failure.

Mr. Osomatsu is a fun, chaotic, and unapologetically absurd take on adulthood and family life, offering non-stop laughs while reintroducing classic characters in a fresh and bold way.