No.9621641 ViewReplyOriginalReport
Hay /a/, theory time,

I think Shinichiro's mom lied. She's probably like Aiko, in love with Harumi's dad, but forced to settle with second best because of Harumi's mom.

Now that the kids have grown up, and she realises that her son is in love with Harumi, she lied to keep them apart from each other. Since you know, regardless of how /a/ approves, it's still a taboo.