I don't understand the fixation with virginity in porn games no matter the situation. It's like so many people feel the need to be the only character doing all the fucking or else the fantasy just doesn't work for them. I get it with corruption games, where it's all about being the first experience for the corrupted character, and I understand the general dislike for NTR because most of us don't enjoy the idea of sharing our love interests. But in games like this and specially with characters like Erika, who's clearly all about feeling free, away from her father's control and experiencing new stuff, it makes total sense that you're not her first sexual encounter. I mean, you're the main character in a harem porn game. You're destined to win. Who cares if some of the girls had sex with a few people before meeting you? It's actually more realistic and helps with the suspension of disbelief.
Also, this is just my personal opinion, but having a character who's had previous experience fall desperately for you feels awesome. It's a confirmation that you're better than the rest.
That being said, I'm thoroughly enjoying this game. The story is rich and interesting, and the characters feel complex. MC is a little awkward, but I'm totally ok with it. It's a great twist to the standard "meet your secret family after your father's death" where not everyone's related and it's not just an excuse to have an easy semi-incestual situation. Even the decision not to say anything feels believable for a person who just lost a loved one and is looking to feel "at home" again.