The Demon Princess Recognizes Me as Her Younger Brother

A story about a young man in Blue Star who admired the moon at 12 o'clock when the Mid-Autumn Festival was about to pass. After going back to sleep, he was led by the system to travel to another world, and his body became the size of a six-year-old. Demon Princess 'Be my brother, I'll give you everything you want' "Okay" The introduction is too weak, please move to the main text.