For the less-informed and would like to know where in the world the things in the fic are coming from, there is this accompaniment thing I draft up that is sorted by parts but isn't really comprehensive and sometimes isn't entirely relevant, but oh well.
Disclaimer: By no means are the following information claimed to be The Truth, since with regards to this particular fandom it simply is impossible to prove (or even 'exist', in my opinion). Writing based on some form of canonical reference is simply a personal preference. As for the authenticity of the information, most of it are result of casual research, i.e. I didn't verify them or keep track of the sources I got them from, but I didn't make them up or jumped on the first thing Google turned up either.
Part1:
In SGZ, it is said that "Zhou Yu lent a generous residence for the Sun family to live in and paid his respects to Sun Ce's mother [Lady Wu] daily." Lady Wu is also quoted to have said that "Zhou Yu is like a son to her".
This presumably happens around the time Sun Jian went up north for the anti-Dong Zhuo coalition, the remaining Sun family moved to the city Zhou Yu lived in, and thus he lent them a place to live in and ‘paid respects to Lady Wu' instead of Sun Jian.
Sun Jian was said to have at least two wives, both Lady Wu's, who are sisters. This "Mother" is referring to the one that apparently gave birth to Shangxiang and another son, and isn't Ce and Quan's birth mother.
Part2:
After Sun Jian's death, Sun Ce served Yuan Shu for a brief period of time before setting out with a small army to set himself up as an independent power. He wrote to Zhou Yu and the latter brought soldiers, horses, etc, to meet him. Sun Ce was described as overjoyed at his arrival. The quote "With Gongjin's help I'm sure to succeed!" is from SGZ. ... It sounded fine in Chinese.
Zhou Yu's merits on the battlefield is also substantiated by Sun Ce's granting of promotions, rewards/gifts and his listing Zhou Yu as the one who achieved the most merits within his army in his memorial to the emperor. He did proposed tactics, fought on battlefield, and recommended people like the Zhang brothers, later some of Wu's highest civil officers.
The scene of this particular reunion was largely inspired by a Chinese fanfic I've lost the link for.
Part3:
Zhou Yu's involvement in the Taishi Ci episode was recorded as such:
- Taishi Ci and Sun Ce dueled to a draw. Taishi Ci's side came up with a reinforcement army. Sun Ce had just a handful of officers and followers. Zhou Yu arrived with a reinforcement army in time to recover them to safety.
- Sun Ce brought troops to engage the encamped enemy. Before the two armies actually went into full-scale battle, the enemy retreated having heard that Zhou Yu had led the rest of Sun Ce's troops and conquered their home city. If memory serves, this was pre-arranged, if not another of Zhou Yu's ideas.
- Taishi Ci's lord fled to Liu Biao and Taishi Ci took up defence in a city (?) with some remaining troops. Sun Ce and Zhou Yu conferred and the latter came up with the plan. Sun Ce led the troops to attack the city and surrounded all gates but one. Zhou Yu had set up ambush troops along the path leading from that gate and thus captured Taishi Ci.
The rest were inspired by the quote (SGYY?) that "when Sun Ce agreed to let Taishi Ci go, all (?) his officers were against it."
General Zhang can refer to Zhang Zhao, who has the image of a very cautious man, or if you prefer, random General A. :)
The title "Tiger of Jiangdong" belongs to Sun Jian, if I didn't get it wrong, but it's been generally accepted, in some parts of fandom at least, that it passed down to his son(s), esp Sun Ce,, as terming someone ‘tiger' usually just means to associate that person with qualities such as ferocity, power, etc.
Sun Ce highly valued Taishi Ci as well. It is said that he wasn't treated like a subordinate and instead more of an ally (of more of less equal standing?).
Characterization here was also more or less affected by the Chinese manga series "Huo Feng Liao Yuan" (Ravages of Time).
Part4:
Of course, from the infamous (?) last words of Sun Ce, "If in doubt, for internal affairs, ask Zhang Zhao. For external affairs, ask Zhou Yu." Lady Wu also was quoted to advise Sun Quan to seek Zhou Yu's advice when Cao Cao came to attack. Before this incident, Sun Quan and Zhou Yu also led a (revenge) force to attack Liu Biao and killed Huang Zu, the one who caused Sun Jian's death.
This scenario is simple enough: Cao Cao comes down south, the Wu court debates all day long over resistance or surrender, Sun Quan wavers. Zhou Yu returns to Wu once he heard the news, decides it once and for all, is put in charge (at least as one of the two) of the battle and kicks Cao Cao's ass back up north. If anyone was bothered by the 'betrayal' bit, in SGYY it was narrated that both (and some more) sides of Wu came to Zhou Yu once he returned to make sure he was on their side. Zhou Yu told both of them yes, most believe because he didn't want to hear their arguments, when his intention was in resistance all along (presumed in the lack of counter-evidence). I just imagine the side advocating surrender were none too pleased when he revealed that in court the next day.
Some believe Sun Quan treated Zhou Yu (or Taishi Ci) well, some believe otherwise. Treatment here of course means giving rank and power and generally how valued an officer is considered, and well means if he is given the treatment he deserves. The argument will not be investigated here, though it leans towards the former. The fic works on the circumstantial ‘records' that no matter what, Zhou Yu held rather significant rank under Sun Quan. At best, he was the commander-in-chief of Wu, at worst, he shared the post of commander with Cheng Pu, and that was only during Chibi.
This is also mainly built on the ideas (originating from the Chinese fandom, at least in my case) that besides Sun Ce and Zhou Yu, there were not many others in Wu who had the ambition and confidence to unify China. Briefly, the argument is the swift expansion under Sun Ce (with Zhou Yu) vs the defensive stance under Sun Quan. And Zhou Yu having planned to conquer the West Riverlands as a step towards Wu's unification of China if he had not died on the way, and how Wu appeared to have stopped expanding (except for Jinghzhou, maybe) after Zhou Yu's death.