It's the Taisho era—a time filled with the scent of romance, and people's hearts are still filled with compassion.

Unzen, Sukayu, Unohana, Oshamanbe, and Aso are all ordinary (?) male students at Binan High School, who spend their days lazing around in the clubroom of the "do-nothing club" Earth Defense Club, and live together in the Kurotama dormitory.

One day, while the five are taking a morning bath at the Kurotama dormitory, they notice something slimy moving in the bathtub. When they finally manage to catch it, it turns out to be a talking Pallas's cat named Nuru!

Nuru has come from the distant future with a serious mission to inform them that the Earth is facing an impending threat of destruction. While he says he wants to protect the Earth, he says he's only come to warn them of the crisis, and that it's up to the five of them to decide whether or not they want to fight for the Earth...

Isn't this just an attempt to dodge responsibility? The Defense Club members are suspicious. "If either is fine with you, I'll do it! That's more fashionable!" Unzen enthusiastically says. The five decide to fight with free will, and Nuru transforms them into the Haikara Romantic Troupe using feline science.

Meanwhile, a mysterious trio called the Bankara New Elite Squad are scheming in the shadows. They are plotting to take over the Earth.