Earth Guardian

A middle school boy who lives abroad. One day, he finds out that the Earth's environmental problems are serious through a broadcast.
The protagonist decides to take the lead in protecting the environment and runs to a separate collection center in the village where he lived and starts collecting separately.
According to this world view, each floor of the apartment has a separate collection center, which was created with the support of people who said they couldn't be bothered to go out.
Nevertheless, people didn't separate the garbage and throw it away. The main character worked hard to separate the garbage for others, but he finally reached his limit and asked the garbage factory owner for help.
Upon hearing the main character's circumstances, the boss is handed an "eco-friendly bullet" and a BB bullet so that the main character can protect the Earth efficiently and interestingly.
What is an eco-friendly bullet? - It vaporizes automatically as soon as it's launched and is composed of components that decompose easily, so it decomposes in half a day when it falls to the floor
The boss asks the main character to match the trash people throw away with a bullet and put it in the right trash bin.
The main character departs to the first floor with the determination to conquer the apartment.... (The apartment is a stage game with 10 floors in total.)