[Quick time travel + angelic and cheerful female protagonist + love-minded and yandere male protagonist + system]
Note: There are very few parts about the system. The heroine is a cheerful and kind-hearted little girl, but the plot is both sadistic and sweet.
The first world: Doomsday vase with academic system
Nian Ruyue: No! I don't have a top-notch system, so why do I still look like a fool? Oh! It turned out to be infected by zombies.
Bai Yu: Wife, long time no see. Uh-huh, I miss you so much.
Slow zombies vs. The patient and yandere professor.
The male protagonist and the female protagonist are happy if they are ordinary; if there are two male protagonists and two female protagonists, so what? What about forced love?
The second world: The inner demon master with cheating system
Nian Ruyue: No! Brother, are you telling me that cheating the system is for other people to cheat?
Ling Jingyu from the Awakening Plot: Old witch, you are the one who covets my body, and I won't make it easy for you.
Nian Ruyue: Brother! Is it possible that someone has changed and you are targeting the wrong person?
Ye Lanzhou, who has awakened his precognitive ability: Master is my wife, Master is my wife (This person is crazy with joy, please forgive me!)
