She is in my top 5 for sure, very good chara-design, top tier seiyuu and her route pacing was really good. I mean i'm always fan of the "mom fucked by her son's friend" thing but the fact that Eri is always waiting for her husband and her son to go out of the house to call Yuuma is just so arousing. She even make sure to send her family far from home on purpose so that she can enjoy days of sex with Yuuma. By the way if you liked the eroge you really need to check the 3D video made by the same guy. It's called "ともだちンちの元気ママ" and it's the same type of scenario than the Eri route. Same mood, almost same pacing.