The Couch Potato Has a Door to Anywhere

I needed to use the bathroom. How did I end up in the Republic of China era as soon as I opened the door??? “Stop hitting me! I really don't know any secrets!” “Erya, Mother saved you some chicken soup.” “My lady, this servant knows she's done wrong. Please forgive me.” “Uncle Zhang, my parents sold me, but I know that even if my body is smashed to pieces, I'll keep my name pure in this world.” ...(The post-apocalyptic era, ancient times, the interstellar age...) Leveling-up story + laid-back heroine + doors to any space