Yes, Erynn did have right to have sex with her boyfriend Zane and Ethan made bad move on recording them. IRL in some states that's illegal and you could end upd in jail. However, even though Erynn is my fav girl here, she is stupid. She blindely believed Ethan that have sex tape of her and Zane without ever seeing video. On her own she never got this idea to set up Ethan and get his confesion, like audio and video tape, perhaps some witness like Alexis or someone neutral and report him to the cops. And this is the part that bothers me. She waited her knight in shining armour (MC or someone else) to save her because she can't figure things on her own. I doubt that even Zane is aware of the video and i wouldn't blame guy if he didn't want to have anything with her because of the way Erynn threated him, ditching him on prom without proper explanation or even telling him that he also is in this video. She imidiately concluded that Ethan and Zane probably conspired so Ethan could get his sex tape.
Edit : Just corected Zach > Zane
This is typical game/avn behaviour in which the girl needs the knight in shinning armor to solve all her problems before they can date.
No wonder people have no patience(and can spot plotholes) for this storyline because it's such an old school and predictable way to to write a romance/relationship start.
The weird part is that only Erynn has this kind of storyline, everyone else is about juggling the different girls and how they are connected to each other, this is when the game is firing on all cylinders in my opinion.
Makes it worst that dealing with Ethan badly stalls Erynn's romance progress while everyone else is free to have a go.
The structure of this game is also kind of unsuited to this blackmail/police topic... because here you are trying to get rid of this problem as soon as possible to get to the good part... and you never know if the next chapter will ignore the problem completely.
Case in point she reveals the issue to us only in episode 7(that's already a long wait btw) and it isn't relevant in episode 8, no steps forward at all in this story and Erynn is completely absent from 9(time to focus on ther girls)... things that as i said stall the whole romance path with Erynn.
On a complete sandbox game, you can focus on the character you want to solve the issues quickly, leave the others for later... On the episodic structure it's immensely frustrating.
It's not the strongest best written part of this game, serves only to stall progress... i hope it gets tackled and knocked out fast, but i'm afraid it won't.
Hopefully at least some good catharsis on seeing Ethan get his when it finally comes.
