Sion no Niwa takes place in the Sion Botanical Research Institute, which is visited by those afflicted with mysterious diseases. The main story is divided into four parts. "Spring: Symbiosis" follows a girl with mysterious regenerative properties and her older brother. "Summer: Midsummer Ocean Night" follows a young boy; within his body grow plants. At night, he is charmed by a mysterious beauty, but he cannot meet her. "Autumn: One Night, One Thousand Years" follows a woman who loses her memory every 15 hours. Meanwhile, the mysterious fungi that grows in her body begins to subsume her. "Winter: Renatus" follows a man who recently received a heart transplant and now lives in loneliness. Inside a dream that takes place in a strange bamboo grove, he witnesses a girl who who flees from him.

(Source: Comic Natalie, translated)