Bosanimal follows the daily adventures of a group of animals that live at their own pace in the human world even if it can be a bit messy and lazy at times.

Tsukasa Atsumi is a salaryman who leads an ordinary, solitary life. On his way back from work one evening, he is saved from a demon attack by a mysterious woman in a ninja outfit. Introducing herself as Shizuri Ideura, she claims that demons target people like Tsukasa, who have Samurai Blood in their veins, and that her kind have been protecting them from the shadows. Told by Shizuri that the attacks are going to become more frequent, Tsukasa makes a deal to provide her with housing in exchange for his safety. To his surprise, he quickly finds out that Shizuri is a shut-in who loves to play video games whenever she is not busy with her ninja duties. As the two spend more time together, Tsukasa grows to appreciate Shizuri's company—and his feelings just might be mutual.

Anhe, the most mysterious killer organization in the world, is composed of the three surnames Su, Xie, and Mu. Everyone was poisoned, and their lives were at stake. After learning the news, the three forces of the Anhe River took the opportunity to launch a rebellion. Su Muyu, as the leader of Spider Shadow's guard group, brought in Bai Hehuai, the genius doctor of Medicine King Valley, to heal the elders, while repelling the killers and protecting the elder Zhouquan. At this time, his friend Su Changhe in Anhe, but on behalf of the Su family joined the operation to assassinate the patriarch.

Ever since the quiet and timid Reina Aharen enrolled in high school, she has made new friends and even started dating her classmate Raidou. When the two begin their second year, everything seems to be going well, as they are seatmates once more. Soon after, a transfer student named Riku Tamanaha joins their class. Unbeknownst to Reina, the outgoing and stylish girl is actually a childhood friend she separated from years ago. With Raidou's support, Reina is able to rekindle their friendship. Although they have grown closer, Raidou and Reina still struggle to communicate due to his overactive imagination and her difficulty with expressing herself. Nevertheless, the eccentric couple continues to brighten up the lives of people around them as they enjoy each other's company to the fullest.