True, the game does have some similarities to Noxian Nights.
But NN was a game where the main character didn't really have any other goal than revenge, like Riven didn't actively look for any teammates or alliances, she just kind of got them due to their goals aligning.
When it comes to character building, then the personality of Riven and Ahri seems quite similar in some ways, the same goes for Xayah and Irelia, but Soraka is very different compared to Katarina and LeBlanc.
Noxian nights had the character designed in a classic way with a 3 man core party, where 1 is aggressive/dominant (Katarina, though she does get dominated herself by more dominant males), 1 is neutral (Riven) and 1 is mild/submissive (Irelia).
The way Ionian corps is atm. is having 1 neutral persona (Ahri), 1 Aggressive/submissive (Xayah) and 1 mild/submissive (Soraka).
The stories aren't very similar.
Ahri is actively looking for her teammates, and isn't out for a personal vendetta that she is actively willing to die for.
The intro isn't really the same in any way as well, as she didn't lose her experience, and she actively sought to get to the place she wanted by catching a ride with a ship. Ahri also has no problem with killing noxian soldiers, and even eats their souls.
There is a fort that she has to go to, that is true, but riven didn't just go there after a short while, and that fort is vastly more important in her story, also she had the "shack guy" (truthfully the real MC of NN, bless shack guy) whom she had no choice but to stay with every day, until way into the story.
Ahri doesn't have that, and Ahri isn't isolated to mainly 1 city where she can roam, there is a world map, and camping.
In ionian corps there aren't any special strong monsters either (or at least not atm), that she could lose to, to get a game over h-scene.
Ahri is also in disguise, and she, as well as the others, can feel who is a friend, due to some potion.
So the main similarities for the 2 are the game they are both based on, as well as the MC's core personalities and the fetishes that are put into the game.
And to be honest, even if it became nearly a clone to NN i would still play the shit out of it, as everyone has already stated NN is a great game. Making another one like it, would be great.
P.s. Not attacking anyone for pointing out the similarities. I just wanted to point out the differences as well.