It could be Orochimaru. He's always been after powerful ninja tools and the Shusui Sword would be no exception. He might want to use it to enhance his own jutsu or gain more power in the ninja world.
One idea could be a story where Naruto discovers the Shusui Sword in an ancient hidden temple. He has to learn how to master its power, which is tied to an old ninja clan's secrets. Maybe he has to face off against a new enemy who also wants the sword for its power.
Fan Xian successfully obtained the key by breaking into the empress dowager's bedroom at night and stealing the key. He used the key to open the box left by Ye Qingmei and found a sniper rifle and two letters inside. Fan Xian had chosen to barge into the empress dowager's chambers at night because he knew the key was in the empress dowager's hands. Fan Xian did not return the key. Instead, he made a fake key and put it back in its original place to avoid arousing the empress dowager's suspicion. Thus, Fan Xian successfully stole the key.
Well, it could be a rival seeking power or someone with a personal vendetta against the empress. There are several possible suspects, and the author might keep us guessing until the end.
'The perfect opening stole the Huangtian Emperor' was a web novel creation meme. It referred to a new web novel in which the author stole the setting of the main character Shi Hao from 'The Perfect World', and used it as the beginning of his own novel. This kind of behavior was considered to be disrespectful and an act of copyright violation to the works of other authors.
In online literature creation, respecting originals and copyrights was very important. If you wanted to create a new novel, you could use your own imagination and ideas to create unique characters and storylines, rather than directly copying or stealing the settings of other works. This way, not only could the quality and uniqueness of the work be guaranteed, but it could also avoid copyright disputes and legal risks.
Well, it's hard to say for sure. It could be a rival manga enthusiast who wanted to have it for themselves or a thief looking to make a profit by selling it on the black market. There are so many possibilities!