Honestly, the only good option here is Erika. Sachi has a horrible personality, she only thinks about herself and is very obnoxious most of the time, and how the fuck does she suddenly like him romanticaly when they've been siblings their whole lives, japs are weird man. And Hiro is even worse, saying she's engaged and whatnot but still keeping him interested enough in her to not go with the other two; she even says to Erika that she's wants to take him for herself, literally a manipulative
. I think I'm pretty much done with the series, shouldn't even be a harem, author didn't need to bring the little sister into it. And no I'm not typing this because I'm some Erika fan, I just think it's the best option considering their chemistry together and how it's a balanced relationship with how both of them care for eachother equally.