Characters in games can be sexual, and sexy. No one is saying that isnt allowed or even complaining about it, and some even champion its inclusion with positive examples such as 2B, Catherine (the transphobia argument is an entirely different subject), Bayonetta, and Ann From Persona 5.
The popular argument is about the gratuitous objectification in the sexualization of women in games, ie, just having women as eye candy, that have shit writing and barely any thought put into the character.
Nothing I see from Niao Sun implies there will be any outrage as far as I can tell. She appears to be a badass, who just happens to be sexy. No complaints. Now if she were to be wearing thongs amd pasties and just serves as a dumb plot device which Ryo has to overcome, and its a complete joke (Quiet), or overly tropey yeah, I can see that causing a bit of controversy and to be honest, I wouldnt exactly say it would be entirely unwarrented. Thankfully there is zero evidence at all that that will be the case. Thus no "Gamer outrage" as you call it.
People are more likely to complain that Shenmue isn't fun and should not exist at all than complain about a character that happens to be sexy.
