That Year, That Day, That Thing in the Time-Travel Novel

Hello, my name is Kodakya. You can call me Traveling Frog, or you can call me System. I have many identities, including supporting roles, villains, protagonists, and the mastermind behind the scenes. In fact, I prefer to be the system or the grandpa. I don't have any reason. I'm lazy. If you have a good chance, give me something small and act. Be grateful to me. Don't be too happy. (No heroine)