Monster Harem In The Tower - Chapter 26: White Flags on the River

After her mother’s passing, Tabitha Collins’s father marries a new wife and sends Tabitha Collins to live with a family she barely knows. There, she meets Alexander Foster, the family’s high-flying Eldest Young Master, who wants nothing to do with her. Apart from him, however, the other members of the family loves her and dotes on her. Soon, things began to change. Alexander Foster becomes intrigued by the mysterious and seemingly untamable Tabitha Collins. Who is she exactly? Initially, the girl seems to lack confidence and needs protecting, but as he finds out more about her, he realizes, he's the one with the catching up to do!

On an ordinary day, Lucius stumbled upon a strange, run-down shop. At first, he assumed it was abandoned—until he stepped inside.[You have entered the Universal Alchemy Store.][Congratulations! You are now the store’s owner.][Please craft your first potion.]Lucius blinked. 'What kind of joke is this?' But as if guided by an unseen force, he followed the instructions. Minutes later, his first creation was complete.[Love Potion: The drinker will fall in love with the first person they lay eyes on.]Lucius swallowed hard. 'Wait… does this actually work?'Before he could process it, the shop’s door swung open.Standing in the entrance was no ordinary customer—she was an elf. Long, pointed ears, mesmerizing green eyes, and a body sculpted by the gods. A visitor from another world.A dangerous thought crept into his mind.'Should I test it on her?'

One day, Luo Jian woke up from his sleep and found himself in a locked chamber where the door and window were all sealed. A note with a few lines written on it was tacked to the wall: “Escape from this room within an hour, otherwise, you will die.”

There is a sequel called Reincarnation Night (轮回之夜) that takes place in the same universe but has different main characters

- Description from Novelupdates

It was always Elliot's dream to become an Adventurer.He lacked magic powers to which was why society looked down on him.His life changed when he was lost in the Forest of Gray Lake, and a book found its way into Elliot's hand. The book was a manual to become strong.So strong that you could cross the level cap of all adventurers.A book that contains the secret to surpass level 100.