Oh, Tama! takes the reader deep into the haphazard lives of Natsuyuki, the protagonist, and his loosely connected circle of dysfunctional acquaintances and family. Trying to keep some semblance of order and decency in his life, working as an occasional freelance photographer, Natsuyuki is visited by his delinquent friend Alexandre, who unexpectedly entrusts him with his sister's pregnant cat, Tama. Despite his initial protests, Natsuyuki accepts his new responsibility and cares compassionately for Tama and her kittens.
Half-sister Tsuneko, meanwhile, is herself pregnant by one of several lovers, all patrons of the bar she runs. She contacts three of them, claiming each to be the father, and demands money. One of these is Fuyuhiko, the older half-brother of Natsuyuki, although he is not aware of this fact. When Fuyuhiko comes to Tokyo in search of Tsuneko, he gravitates to Natsuyuki's apartment, where he and Alexandre move in with the weak-willed Natsuyuki.
Half-sister Tsuneko, meanwhile, is herself pregnant by one of several lovers, all patrons of the bar she runs. She contacts three of them, claiming each to be the father, and demands money. One of these is Fuyuhiko, the older half-brother of Natsuyuki, although he is not aware of this fact. When Fuyuhiko comes to Tokyo in search of Tsuneko, he gravitates to Natsuyuki's apartment, where he and Alexandre move in with the weak-willed Natsuyuki.
