As far as I was aware, the closest Honkai: Impact 3rd media got to explaining how Welt Yang got to Honkai: Star Rail was the Alien Space comic, which she had read solely because it was part of Welt Yang's backstory. Alien Space took place in 2029, given it was 2014 now, that's at least 15 years that she would have to wait, and given how the ending of Alien Space wasn't aligned with Welt's travel to the HSR universe, it could be even longer. At the end of alien space both Welt Yang and Void archives, in one of Otto's realistic soulium bodies, find out of the existence of another Murata Himeko, this being the one from HSR. After discovering the existence of this alternate Himeko, and in the interest of changing their fate from the Himeko that existed here in HI3.
So, Lee presumably had to survive at least until the year 2029, befriend or threaten Welt or Void archives into taking her with them. Right now, Void Archives was with Otto, and she was unlikely to be able to gain access to talk with it unless she was willing to give up some information that she knew about the future to Otto, which she wasn't sure of yet. Welt Yang was at St. Freya academy, investigating this new project that Otto approved to see if it was anything malicious, all while failing to uncover the secret research facility into Schariac Holy Blood underneath the school. He was easily befriendable, or blackmail-able , given his precarious situation of being undercover, and his situation would only get worse. Welt Yang was "killed" and forced to give up his Herrscher core to Bronya Zaychik, leaving him even weaker than he was before with his even admittedly quite pitiful core synchronicity.
If she could join St. Freya, she could easily gain access to Welt Yang, and do whatever it is she needed to do, however there were a couple problems. This assumed that the butterfly effect from her arrival and subsequent actions did not change anything that led to the derailment of the main story and timeline, and that everything happened exactly how it did originally. This was improbable. The second problem is the 15 year wait. Lee was not exactly the most patient person, and being trapped in this world for a whole 15 years getting attached to this world before abandoning it never to come back again was not exactly the most enticing prospect.
There was always another route, trusting Otto.
While this initially seems like a terrible idea given knowledge of Otto's activities, with all possible given information, it was one of the better paths to choose. Otto had both the knowledge and resources to help Lee get to the world of HSR, he had, or will eventually possess the second divine key, which should presumably be how both Welt Yang and Void Archives managed to get to the world of Honkai: Star Rail to begin with, unless the sugars somehow managed to loose both Welt Yang and Void archives while traveling back to earth… actually that might have happened, they didn't seem that reliable.
In other words, there was a complete lack of information regarding Welt's Journey, so proactively trying to seek methods for traveling to the world of HSR would probably be a better path.
Plus she wouldn't have to wait 15 years.
The best method for convincing Otto to help would be to give them information about the Cosmic Juggernauts true location, in imaginary space above London. This was a necessary step in the plan, presuming it required the Cosmic Juggernaut, which it probably did, all while gaining Otto's trust, and not even breaking the timeline to much, given how Otto was bound to end up with the Cosmic Juggernaut in his possession anyway.
The best method for contacting Otto would probably be Fu Hua, who was also at St. Freya. She possessed a direct link to Otto in the form of those ugly ass glasses she always wore while at St. Freya. Seriously with all the advanced technology at Otto's disposal he couldn't make it look less terrible? Lee would just have to reveal to Fu Hua that she was well aware of her identity as a spy, and request a conversation with Otto himself.
Hopefully not having my memories altered by Fu Hua through the Fenghuang Down. Speaking of which, Otto possessed the Key of Revelation, where Void Archives resided, its primary function was its ability to create copies of anything in the archive of void archives, including divine keys. This included the Key of Sentience, which Otto could use to peak inside her head, she would have to resolve that.
System, can you block someone from accessing my memories?
[System: Sorry, Systems employed by the Sentari Systems corporation are not allowed to perform any action related to the mind after the passing of the Protectee act, I would not be able to block access without being able to access it first. (ᵕ—ᴗ—)]
Well good to know, that's probably a good thing, otherwise the system might force her into romances she was not prepared for at the moment.
[System: Even if I could, I wouldn't do that! It hurts that you think of me in such a way. (╥﹏╥)]
She could always help Fu Hua in some other way and request that she help create a mental barrier to block memory reading by convincing her that she would eventually need to face the Herrscher of Sentience, since the order of Herrscher's was fixed, and the world had technically undergone Herrscher's 1-5 in the form of Welt Joyce and Sirin. The Herrscher of Death was also set to be Seele, who would be drawn into the Sea of Quanta after the X-10 experiments and cut off from the Cocoon of Finality and the Will of Honkai.
The will of Honkai, that was an interesting thought, she could always attempt to pull an Otto and attempt to work with the will of Honkai to expel herself. Surely it wouldn't mind helping kick out an outsider that could potentially cause drastic problems, one way or the other. Something to consider if they ever showed up.
So after the attempted rebirth of Sirin, the next potential Herrscher would be the Herrsher of fire according to the previous era, and then the Herrscher of sentience. That would be if Promethus didn't manage to fuck up one of its only 2 jobs, which was to activate the project Stigmata Finality backdoor at the right moment, and to ensure the order of the Herrschers followed the same order as the previous era. 3 jobs if you count ensuring that no new weird Herrschers show up as well.
I could convince Fu Hua that it was inevitable that I would need to fight the Herrscher of Sentience, and that I would need to create a barrier to prevent it from changing my memories. That might not work though, while Fu Hua was easily manipulated by Otto, she would definitely be on guard with someone she had never really met before. She would also not be in an extremely brain damaged state when I met them for the first time, so building trust might be a bit difficult.
I could always tell the truth that I wanted to work with Otto, and that I planned to trade some information to Otto in exchange for his help in returning "Home", and I was worried that given his personality and extreme interest in obtaining the information I had, he would easily attempt to read my memories to gain access to that information without paying. While Fu Hua took orders from Otto, she never really trusted him fully. In addition, I was pretty sure Fu Hua was unaware that Otto held the Key of Revelation until the moment she got shot in the head with it. It was too big a trump card to be revealed easily.
Wow, all this thinking was really making me hungry, and I was still somewhat dizzy from that teleportation earlier. I should probably find somewhere nice and sit down, and maybe take a good rest.
Walking out of the alley, she immediately saw Kiana Kaslana again, turned around, and walked straight back into the alley.
Fuck, totally forgot she was right there, I am definitely not prepared to interact with her.
Suddenly, she heard footsteps behind her.
She turned — and froze.
Kiana stood at the alley entrance in her Chiba Academy uniform.
Oh, hell no.
Lee's brain screamed, but her body did nothing. Ten agonizing seconds passed before Kiana tilted her head.
"Uh… are you okay?" Kiana asked, "You lost or something?" tilting her head. "Saw you enter and exit this alley twice. Plus, I heard you yelling something strange earlier."
"Oh, you—uh—heard that?" Lee said, heat rushing to her face. "Whoops. Yeah, I'm lost."
Great. Fantastic. Perfect first impression. Just scream prayers into the void where people can hear you.
"Was trying to get some food or something," she added, trying to sound casual.
Kiana grinned. "Cool. I am already skipping school anyway. Wanna grab lunch together?"
Lee hesitated. On one hand: stranger danger, timeline risk, and general panic. On the other: this was Kiana Kaslana. Whether she liked it or not, getting close to her was probably the smart play. As a normal person, she could always 'die' later.
"Sure," Lee said finally.
As they started walking, Kiana sniffed dramatically. "Huh. You smell nice."
Lee nearly tripped over her own feet. "Uh—what?"
"I dunno. You just smell really clean. Like flowers or something."
Lee's brain short-circuited. Great. Just great. Day one in another world and she was already getting called out by anime characters.
They walked in awkward silence for a moment before Kiana glanced sideways at her. "You feel strong."
Lee blinked. How the hell can you just tell that? Are you some kind of animal? Normal people can't just sense that.
Out loud, she said, "I don't think I'm stronger than the average person."
Kiana shrugged like it wasn't a big deal.
They stopped at a small food stall. Lee pointed at something simple on the menu, trying not to look as rattled as she felt.
[System: This is a perfect opportunity to start building intimacy! Maybe compliment her hair? Or say something flirty—]
Nope. Not doing that.
[System: But flirting would boost affinity! (✧ω✧)]
Nope. Nope. Nope.
Not Now.
Lee paid for both meals before Kiana could argue. As she pulled her wallet back, Kiana caught sight of the ID in the clear window.
"Chiba Academy?" Kiana said, pointing.
Lee nodded. "Yeah. I'm transferring there soon."
Kiana's eyes lit up. "No way! Guess I'll see you around then."
Lee forced a smile. "Yeah… guess so."
Inside, she was already wondering if this was a mistake.
After they finished eating, Lee stood and brushed herself off.
"I should probably get going."
Kiana looked up at her. "Oh, sure. But hey—give me your number or something. We should hang out again."
Lee froze. "Uh… I don't have a phone."
Kiana gave her a flat look. "Who doesn't have a phone?"
Lee sighed and pulled her shattered, half-lit phone from her pocket, holding it up. "This one's broken."
Kiana leaned closer and blinked at it. "Wow. That thing looks ancient. Where'd you even get a model like that?"
Lee's eye twitched. Of course it looks ancient. Different world, different tech. Great.
"I was going to get a new one," Lee said quickly.
"Oh! I can show you where to buy one," Kiana offered, already half-standing.
"No, no, it's fine," Lee said, waving her off. "I'll figure it out."
"You sure?"
"Yeah."
With a casual wave, Kiana wandered off down the street, leaving Lee standing there, feeling the silence close in around her.
After a long moment, Lee muttered, "…I have no idea where I am."
Her gaze darted over the unfamiliar streets, the bustling city, the faint smell of street food still clinging to the air. She didn't know where to buy a phone. She didn't even know where the Academy was. And she definitely didn't have a map.
"Faaantastic," she groaned, shoving her broken phone back into her pocket.
[System: You could ask someone for directions! (≧◡≦)]
Yeah, sure. Or I could embarrass myself in front of even more people today.
Lee exhaled sharply and squared her shoulders.
"Okay. Step one: find a phone. Step two: figure out where the hell Chiba Academy is. Step three: find a place to stay."
Her stomach growled, loud enough to make her wince.
"…Maybe step four: eat something that isn't fried mystery food," she muttered, setting off down the street at random.