Tokisaka-san wa Boku to Chikyuu ni Kibishisugiru.

Utsugi Souya avoids attention and prioritizes following rules, particularly those related to environmental protection. He is meticulous about recycling and has even been late to school to properly sort waste. One day, he discovers his trash has been left behind due to improper sorting. Someone deliberately mixes his trash daily, so he sets a trap and catches the culprit: Tokisaka Koyomi, a new classmate who claims to be from the future. She explains her mission is to stop all eco-friendly efforts. As a result, Souya and Tokisaka are forced to live together and work against environmental causes so she can return to her time.